Philosophy of a cheapskate
In terms of vocals, I can't say because I tend to think that if you're fairly close to the mike, the room will have less of an effect although as I write that, my mind flies to the idea of recording in a cavern......that would probably carry echo-y-ness or long decaying reverb. And there are spaces where you can get a horrid ring if you're singing loud enough. Depends what you want, really.
But in terms of instruments, the space you're in can have a major impact on what's recorded, depending on how you record and where you place mics. I was playing in this vast circular auditorium four days back (I was jamming with my friend who does some janitor work there) and while he was setting up his drums, he gave some whaps on the bass drum. I tell you, it sounded like a cannon going off 50 feet away. I've played in that place a number of times but most of the time it's been full of people and though my mate has told me for years it's a nightmare of a place to play, I'd never noticed it until last tuesday. I kept getting him to whap the kick and I couldn't get enough of that awful echo. The delay was like one and a half seconds, with an additional PPSSHHEEEOOOWWW that followed. It reminded me of a hugely amplified bassy version of my kids' heartbeats when they were in the womb and my wife was hooked up to this machine that enabled you to hear them !
One of the most recurrent themes in HR is that of room treatment. People mention it so much that after a while it can drive one caramba. But then,
we aren't in those rooms and recording spaces of the main advocates so one can't really say if it's an exaggeration. I think maybe those that talk alot about it have good reason to and those that are a little less vocal are perhaps more fortunate and have more natural absorption, reflection and whatever. I'm inclined to not disregard either party. Also, you get varying opinions on size and shape, some advocating burning down your square or cuboid room

D) while others say nah, you can get good results in a cube. While I'm inclined towards the "anything is usable" philosophy of a cheapskate

I also acknowledge that other views are just as valid and that there are good reasons for them. And the final outcomes you're going for weigh heavilly in this.
In the end, your ears are what will be the final arbiter. You could try recording some scratch vocals in a variety of even household locations and distances, like a kitchen, a toilet, a bathroom and a closet and as you listen back, close your eyes and compare. You'll start to maybe have some idea of what, if anything, needs doing and what differences there may be.