Lots for you to think about! You probably already know I'm dog mad, have a deal of experience with my own family dogs, walking and training dogs for others, and @Rocky998
can vouch that I'm pretty good at looking at a mutt and picking out what breed mixes are likely in there! So once you're at the point of looking at pictures of dogs, I'm more than happy to take a look and see which breeds I think are likely dominating - and others here like @Alice B
are good at this too, so making a thread with photos of the dog(s) you have in mind could give you a good idea of the things you might expect from the specific dog you get.
You're right that while purebreed show snobbery sucks in so many ways I won't go into now - breed does give you a good indicator of both what the dog will need from you, and whether it would suit you and the lifestyle you have planned for you and the dog. Breed traits are just traits, not certainties, but since we bred and shaped these dogs for specific purposes, we didn't just breed for shape, coat and colour, but elements like temperament, drive, heightened or shortened hunting sequences etc. So it's wise to browse some breed profiles and see what you really do, but importantly, really don't, want.
Most dogs in the size range you're wanting could clear a 3-4 ft easily. Some breeds are more prone to escaping too... huskies, malamutes and collies can clear a six foot fence, and if you get a hound type with a high prey drive, a rabbit or deer they want on the other side of that fence means they'll be gone. Go larger if you can, or look into dog safe fencing that curls inwards at the top. How much of an escape artist the dog may be is hard to predict. My Springer/Collie could easily clear the fencing in our garden when she was younger, if she'd wanted to, but I'd worked on her recall and respecting the boundaries since she was a pup (nothing negative, just calling her back to me and rewarding when she came) so she's never tried to escape the garden, or roam too far from me. Never had problems with the Jack Russell, Springer/Cocker, or black lab/whippet either.
It's easiest to build a strong recall when it's a pup that is still in that puppy elastic stage, where they don't want to be too far from you anyway, but can still do it with an older dog. But some breeds have a much stronger prey-drive, or are bred to work independently, and so can go selectively deaf, and are much more likely to hare away chasing something. Sighthounds and scenthounds, most often.
Rather than a specific breed, think about the groups that the dog belongs too. What sort of work it was bred to do. This helps with training too. The way to motivate and what activities to do are completely different with my Springer/Collie than my friend's retired greyhound. When you know what drives the dog is likely to have due to it's breed mixes, you can harness those drives both to make training for what you want easier, and to enhance the dos life. If you adopted a rescue beagle, then learning how to do simple scent-work will both make the dog very happy, and tire them out. For any dog, mental exercise is just as important (and tiring!) as physical exercise, so you need a balance of both.
I'm biased towards the gundog group, which your goldie belonged to. Avoid labs since you don't get on well with the oils - I think that should probably rule out staffies and other bully breeds, rotties and dobermans, since they tend to get that oiliness too, as do shepherds sometimes, although less so with the shepherds if the coat is maintained well. They shed like the devil too though.
The duck tolling retriever might suit you very well- you should definitely read up more on them! I'm jealous, I'd love one of them.
But also consider the spaniels and setters, maybe pointers too. Something like a German Short-haired pointer might set off your oily coat reaction, but the wire-haired would be better.
The good thing about gundogs is that they're active and fun, but also biddable and tend towards being very trainable, sensitive to working closely with their human, so they watch you for direction usually. Their prey-drive tends to be less than in many other breeds because they've been bred to flush game for the gun, not kill it themselves, and soft-mouthed to hold it gently when fetching it so they don't damage and ruin the game. This makes them pretty great family dogs and around small kids.
Downside to setters/pointers/spaniels is higher grooming needs, but trimming the feathering and stripping any loose undercoat every three months or so keeps it much more under control and makes the daily/every other day grooming a pretty simple brush over to remove dead coat. They do shed, but it's not as bad as with a goldie/lab/shepherd.
Energy levels for the above can be a downside, and also something that can vary a lot (especially show lines vs working lines). It depends on age/breed/what you do with them. Springers for example are very bouncy and keen to go out and do something, so if someone is occupied with a young family and only able to walk the dog once a week, they'll soon struggle with a bored and unhappy dog that might well be destructive, even if only from bouncing off the furniture. But in your case since you have a good amount of space, if the dog gets out on a walk twice a day, has some tennis boys and toys to play with, and you spend some time with it every day, maybe teaching some basic obedience or trick training (short five minute training sessions are best) then you'll have a very happy gundog.
While letting dogs out to run around on land is exercise, I don't count this as a walk. Walking with their human is very different, much more rewarding, and I play games and train as I walk them. It breaks up any boredom, and keeps the dog excited since they're not sure what's coming next, but they know it'll be fun
Herding breeds might work well for you too.
Lastly, don't rule out smaller dogs! Terriers have bags of personality, and especially some of the working ones have the heart of a lion. Brave as all heck. Jack Russells, cairn, norfolk, patterdale - and one of my favourites, check out Border Terriers. They look like grumpy little old men, but every one I've ever met has been the sweetest, most easy going little companion that will walk with your for hours, then curl up on your lap or at your feet and snooze away the day while you read or watch TV. Great little dogs, and far from a toy breed.