Won't running lots of utility apps slow down the computer?

I usually like to keep my OS light and without unnecessary apps running in the background (old habit coming from when I used to have a memory-challenged PC as a kid). I switched over to mac a couple months ago and found lots of useful utility apps (e.g., alt-tab, rectangle, alfred) and know that there are lots more apps out there. I'd like to download and try other apps but am worried that having a lot of these running will bog down the computer. In fact, I see Youtubers recommending many different utility apps that all seem quite useful but the thought of having so many different apps running is a bit uncomfortable for me. How many utility apps do you usually have running? Am I worrying too much? p.s. this is a completely unrelated question, but I couldn't find the answer to it. Sometimes, when I'm using Safari (haven't tested it on other apps so not sure if this is a Safari-specific problem), the Safari window will stay on top even when I run other commands. For instance, while using Safari, if I run App Store using Alfred, App Store won't appear on my window. Then, I'd see that it actually loaded but is being "superceded" by Safari, as if I ran App Store but then quickly switched focus to Safari again. I usually just reboot my MBP (again, another habit coming from my PC days), but this happens quite often.. Do you have any suggestions?