Is 3 people on each side of an 8ft table weird? ideally what's the space chairs should have?

Either of those look absolutely fine to me . If all the offer tables are going to be 8ft, I’d probably stick with that rather than swapping one to 6ft ( unless there is some other space saving advantage to losing the extra 2ft)

Either looks fine to me. I'd just consider what works best in the space (8' or 6').

I don't think that's weird! especially now during covid i've been seeing brides spread people out more and more

I would keep the table sizes consistent. Also keep the chair numbers consistent. If you are doing place cards on the table (assigning actual seats, not just tables) then you can place however you want but have the extra chair(s) at the table. If you are assigning tables and not actual seats then you’ll need to have the extra chairs at each table along with the extra placements on the tables.

You can seat 8-10 adults at an 8 foot rectangular table, so you can certainly fit 4 people per side if you need to but 3 per side is also a great fit!! 🌟

I'd stick with two 8 foot tables if it fits well in your venue space!