One of the primary reasons for doing a fishless cycle is that it allows one to stock a tank fully all at once. You just spent weeks cultivating enough bacteria to do this and now what you are asking is. "Should I stock like the tank is not yet fully cycled?"
Another advantage to adding more rather than fewer fish is that it will blunt aggression. This is the same reason for stocking more rather than fewer small fish. It spreads out aggressive behavior such that the same fish is not always getting beaten up. Also, when fish are new to a tank they are all working to settle in. When adding over time, this may give the first fish in the chance to believe it is their tank and they may be more belligerent towards the next additions.
Next, if one adds all the fish at once, there will be no need to quarantine new fish. They are all new at the same time. Experiend keepers know about the need to quarantine new additions before adding them to an established tank. How would you feel if the last fish you add has a disease showing no symptoms and it ends up wiping out the tank?
Finally, fully stocking a tank that has been properly cycled without fish means you should not see any ammonia or nitrite spikes when you add all the fish. But doing it slowly can mean this benefit has been lost and, if one is not careful, you get the very ammonia and nitrite spikes fishless cycling is designed to avoid.
Of course there are some fish which do better in just the reverse they need to be added later rather than all at the same time. But for the most part I have found adding more fish at one time tends to work better than a few at a time.
Next, cycling a planted tank is different than cycling one with no live plants. The reason is simple. Most of the bacteria one does develop when doing a fishless cycle will die off as live plants are added. This is because the plants use ammonia (as ammonium) much faster than the bacteria can use it. However, no matter how many live plants are in a tank, there will still always be some amount of nitrifying bacteria as well. Plants host bacteria. So one can have a heavily planted tank and still have some bacteria. On the other hand one can have a tank with no plants and bacteria does almost 100% of the ammonia and nitrite processing.
Finally, it is important to understand how the bacteria react when the amount of ammonia in a tank increases or decreases. The bacteria only reproduce to create greater numbers when there is more ammonia than they need. This in turn makes more nitrite and those bacreria will also increase their numbers. The total amount of nitrifying bacteria in any tanks depend on the amount of ammonia available. This works in both directions. If we have a fully cycled and fully stocked tank and we remove half of the fish load, over the next few weeks the amount of bacteria will shrink until what remains is what is needed to process the new lower ammonia loading.
All of this works on the individual level. Normally the bacteria reproduce at a rate commensurate with the ammonia load. As one cell dies another one divides and the number remain fairly constant. If the ammonia level increases, more cells will divide than die, and the total numbers go up. This is also how they tend to change where they live in a tank.
If we get lazy and fail to clean a filter, as it begins to clog the bacteria living there get less flow and thus less "food." They will reproduce more slowly. However, since the ammonia loading in the tank has not changed, bacteria elsewhere where circulation is better will reproduce faster. The result is fewer are in the filter and more are elsewhere such that the total remains fairly constant. Because the bacteria need "room service", they tend to live in the greatest numbers where ever that is the best.
When planning a a tank with live plants it is generally best to plant first, let the plants settle in and then worry about the need for any cycling. If one plants heavily enough one can do a silent cycle. This is basically a fish in cycle with plants. So the ability of the plants to handle ammonia becomes the primary filtration for this. Yes, one still has bacteria and as the plants grow and are able to handle more ammonia, the bacteria will also reproduce some. However, the amount of ammonia one should add when there are plants in a tank is less than we would add were there are no live plants involved.
One last observation which most folks do not really consider. Under optimal conditions the ammonia bacteria can double in about 8 hours and the nitrite ones in about 11. There is no way a plant can double in mass in that time. So if the ammonia in a tank increases, the bacteria will react to this faster. But over time the plants will be stealing the bacteria's lunch and the plants will grow and the number of bacteria will decline. With plants, quickly increasing the amount of ammonia they can handle requires that one add more of them.
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