Is my cat introduction going okay?

Okay, so we got this new kitty (1-2 y/o, unfortunately we dont know for sure due to him being a rescue). We also have a resident kitty (17 y/o).

We are at the stage of actually letting them be in the same room. When new cat just enters the resident cat will stare a lil but eventually calm down. New cat is uninterested but chill with resident cat.

I tried watching Jackson Galaxy videos but am struggling to read some of their language, so I wanted to ask for help:

1 y/o: genuinely seems chill. Doesn't approach resident cat. Doesn't seem stressed. No meowing or hissing. No airplane ears. Genuinely just doesnt care.

Resident cat is where im confused: he does approach the new cat to sniff and doesn't stalk him but watches him carefully from a comfortable spot. He lays down and keeps an ear on him (one radar ear in new cats direction). He is wary of being in the new cats separated room but doesnt mind anything that smells like him. He sort of just watches him?

Interactions: resident cat will sometimes come up to sniff but mostly just watch. Will sometimes meow at him but there is no hissing. And its like a singular meow. They dont swat and they CAN sleep in the same room. Just takes the resident a lil to calm down before he does. They are super territorial around food. Aka they can eat in the same room but WILL get pissy over bowls being approached by the other cat.

I just dont know. Is this fine at this stage? Like should I keep letting them be in the same room or do I need to separate them again? Tbh this has been anxiety inducing. I dont want the resident cat to suffer:(