Nope lemons are nice and deep bodied, its more the streamline fish such as neons/cardinals/guppies etc you need to be carefull of. As far as im aware angels dont strictly need to be kept in groups, i believe its just a prefference All depends on the size of your tank.
So do you think that two koi or silver angelfish should be ok together.
also i'm thinking of adding some gouramies, will they be alright with the angelfish?
My tanks ajuwel 96 litre length 81cm height 36cm, width 31cm.
i do believe the minimum height tank you need for angels is 18inches (40cm) yours will be 'just' to short for them, they grow rather large and need height to accomodate their long fins
There is P. leopoldi, but good luck finding one. I've seen them once in my LFS once at the tune of $150 each, which is even more than wild caught altum angels (which are bigger than the common scalare). I know very little about them, except they only get 2-2.5 inches long and have an odd looking up-turned snout.