I wouldn’t just blindly disable start up applications. Some of them are essential and turning them off can create issues. Some others are maybe not essential, but they are so heavily depended on and so expected, that it could create issues, if other programs miss it.
This issue is a fine case of an XY Problem, but at least you did mention the actual issue at hand, so that makes finding a solution easier.
Because of this your attempt at solution Y is already quite futile, since your start-up applications are started after you log in, not before. So even if disabling wouldn’t harm your installation, you would still see no performance benefit.
It is rather advising to check what the actual cause of your long boot time is.
Is it your storage medium?
Is it any other hardware?
When did it start to happen?
What changed on the system just before it started to happen?
Ironically, you did not provide any information on these important questions, as should be expected in a fine case of the XY Problem.
So – if you want an actual solution to your actual problem, start engaging with the previous commentators’ questions and get to answering those and these above in this post.