Will deleting unused Mac and nonMac applications on my iMac speed it up?

Removing unused apps will not speed up your Mac.

And while they do take up disk space, you should not remove apps willy-nilly, especially Mac apps installed along with macOS (Safari & QuickTime being prime examples of apps you should never remove even if you don't use them.)

If it's an app you installed yourself and you want to remove it, ok, but all you will do is free up a bit of disk space.

Hi GPsFriend, strictly that, and that alone...No....not having many apps running at one time....possibly....

I* don't know what exact year and model number+specs of your iMac, just that it's a 21.5 inch iMac, running MacOS 13.4 which is Big Sur or Sonoma, so I'll assume it's pretty recent and new-ish...it's probably an m1 or M2 iMac (Apple Silicon) so it's not upgradeable at ALL, after you buy it.... not by the User, that being you, or by an AASP (apple authorized service provider) or Apple Store with Genius Bar... as it's probably a built to order product, you could have upgraded it before you bought it, but now that you have bought it. no...

John B

It is only partially true that removing apps will not speed up your computer. There are some app that will install processes on startup that will run in the background whether you are using the app or not. This will consume resources and could slow your Mac down. To see what is getting installed on startup and running in the background, I recommend using EtreCheck and post the results here using the Additional Text option. You only need to do the free scan to determine what processes are running that could slow your system down.

Using EtreCheck - Apple Community

If you have a reasonable amount of free space on your drive, deleting never-used apps won't do anything to speed up your Mac. It might reduce visual clutter, if you're sure you'll never want to run those apps again.

When a HDD or SSD gets very close to being full, performance can suffer a lot as the HDD becomes fragmented or the SSD tries to manage free space. Then, deleting or offloading files can make a difference.

If this is a 21.5-inch iMac made between 2012 and 2019, the most common cause of slowness is the slow and under-spec mechanical hard drives Apple fitted to entry-level models. Those drive as simply not keeping up with newer macOS versions.

Removing apps ot adding RAM cannot change that. The option of a faster extern drive is about the only option that does not require profession help and a risk of permanent damage from opening a sealed-case computer:

User-submitted tip: Use an external SSD as your startup disk … - Apple Community