My husband and I purchased a spin bike early in the pandemic after trying (and failing) to enjoy using trainers with our outdoor bikes. Total game changer. This is the spin bike we have (apprx $350 on Amazon right now with the coupon) and I wholeheartedly recommend it.

While I don't have experience with fold up models, I would think they would be a little unnerving to use from a stability standpoint and might limit the out-of-the-saddle movements you can do. And, the bike above isn't that much more expensive in the grand scheme of things.

Also - before you spend money on a subscription to Peloton or whatever, check out Kaleigh Cohen Cycling on Youtube. She has a ton of very well-done spin classes of varying difficulty/length as well as several helpful videos on bike set up, etc. She also periodically does training programs that you can follow in a sequence. All for free!