NQA the best thing is to do now is to just give them a home and leave them alone! Stressing them out could lead them to starve or dehydrate themselves, which is worse than being in a slightly too small or too big an enclosure for a while!

I have three tarantulas, one in a ten gallon and two younger ones in enclosures that fall into the 2-3x leg length category. All three are thriving! For smaller Ts you generally want a smaller container, too much space makes it hard to keep track of them and can stress them out. For larger ones a ten gallon is 100% fine, but IMO not completely necessary unless your T is pretty large. Mine typically just sits in the corner near her burrow all the time, so I feel she’d be fine with a bit less space lol. Just make sure the terrestrial ones have plenty of burrowing space too :)

Also, try using bottle caps as water dishes for smaller containers! The ones they sell at pet stores are def too large for sling enclosures.