Congratulations on the new apartment! My rule #1 for sofas is buy the best quality you can afford. You and your friends/relatives will be using this a lot. Other things to consider: can you lie down on it for sleep? Consider a sleep sofa if guests are anticipated. Don’t select upholstery fabric without seeing it in your room first (I learned this the hard way.) Can someone of all ages get up from it without difficulty? I’m not a fan of modular sofas for many reasons, but the biggest issue I have is with the bulky nature of them that limits free flow around the room. Also, I don’t think your room is big enough. I’d move in first (lawn chairs served many people well until a sofa decision is made), get a feel for the space and how you will use the room. Sit on all possible choices, lie down on them, etc. take a ruler with you to the store and your room dimensions. Again, buy the best you can - you won’t regret it.

IKEA has pieces with pocketed springs and removable washable covers you can change to a different color. You can get a sectional function with a couch with chaise and large ottomans that double as a table.

For US manufacturers Lexington Furniture Co. is a retailer with good pricing by getting products drop shipped. Taylor King is an example for custom. Lex represents them.I like a deeper seat to lay out.

Congrats on your first place. Is there any reason you need to make the purchase before moving in?

Modular sofas can be really chunky. You need to measure the door to make sure it can fit through. I'd wait to purchase until you move in.

Also, what other furniture do you want in this room? How do you and friends or guests spend time together? If everyone crashing out on one bit sofa is what you like, then find a way to make it work. If you want a more standard set up with a sofa and chairs, you need to figure out that layout too.

I usually say but the best quality you can afford. But, for your first apartment, I wouldn't stick to that rule. Your needs, tastes, location might change with time. I'd get something that isn't too expensive and allows flexibility.

Notice how the rug is place in the inspiration photo and how it lines up with the edge of the slider.