I pretty much cosign what dee said. Niether situation sounds ideal but for just recording vocals I suppose the small space with the bed is the better option lmao. As far as headphones, I'd say they'd be adequate for putting your vocals on top of other beats. Adding vocals to an instrumental still requires some "mixing" (arguably vocals are the hardest thing to mix correctly) so monitors would be more appropriate, but you obviously gotta work with what ya got.
Are you adding treatment or something to deaden the room your recording in ?(ie: a lot of vocal booths are completely dead, no reflection,or in case of larger ones you want to kill early reflecti0ns..)
Recording at home / building your own home studio is a long trial and error process, so I'd always suggest trying the cheapest method first, seeing if you like the results, and if they aren't what you were looking for then proceed to invest in what would help (but first do research so you don't buy some shit you don't need).
My 2c