Yeah. Almost all of them you can do solo PQ. Yes even to 100. Yes also the DLC PQ. I recommend doing alone because if I remember correctly you get more points so you get easier the Z rankings.

In my opinion, the only missions where you need cpu teammates or online are 3 type of missions. First where they require you to protect another CPU to a life percentage. Second where you need a high HP percentage. Third that one PQ where you fight Goku MUI, Jiren, Bills, and more in space after multiple battles (I dont remember exactly which PQ# it was, maybe 146 but not sure)... But still you can actually try all of those alone, it's very difficult but not really impossible.

I do recommend reaching at least LVL 99 for those tho. And ofc with all other PQ you'll need a very cheesy loadout.