How many depends on genetics and phenos. It could be anywhere between 4-16 plants in there. Pot size 6 Litres minimum and 17L is starting to be a bit of an overkill, unless you got genetics that grow extra big and you want to grow as large plants as possible, then around 17L pots max. 11L is enough for pretty much everything and around 8L is enough for most. Just remember that small pots means that you need to water more often by the end of life cycle.
Dont aggressively remove anything. You can top autos if you know what you are doing, but especially if these are small plants and you have tons of them, its better not to top. But if you know what you are doing and the plant genes are good for it, you could top them.
If you top, you need to know the right time juuuuust before it starts to flower, or do it right away when the first preflower appears. Then top under that preflower, so that there are no preflowers after topping. The lower branches will mature a bit before the plant will continue flowering.
Often its better to just LST imo, topping autoflowers works best with tight places where the plants need to be short as possible.
I like to remove the first set of branches early on, because they would grow small loose buds anyways and needlessly eat away resources. You could also grow these out a bit and if they get big enough before they start to make flowers, you could clone them and get few extra grams out of each in solo cups somewhere in the corner of the tent. Or you you got tons of them, maybe hook them up on the walls or something