Two slots are enough for 32GB.

Yes. Two 16GB sticks will give you 32GB, and that setup is standard on most mini-ITX boards.

The only thing you need to confirm is that your specific motherboard and CPU support 16GB per slot. Almost any board from the last five years does. Some even support 32GB per slot, so 64GB is possible if you want to go higher. Check the motherboard QVL (qualified vendor list) if you want to be super safe, but any decent DDR4 or DDR5 kit will work.

Mini-ITX is not a limitation here. Two slots just mean you fill them both, no room for future upgrades, but 32GB is plenty for gaming and most work.

Just don’t buy super sketchy RAM. That’s where you get problems.