How do I enable click-and-drag text selection and improve scrolling with a scroll mouse on a new Mac?

Brand new MAC as of January '25. I always used Windows but am determined to learn the MAC. I have noticed 2 things:

1. I can't click and drag the cursor to highlight text so I can copy/paste/delete. My settings allows me to use the track pad to drag but I don't use the trackpad. The mouse has no such option in settings.
2. I have a scroll mouse (EX-6 Elecom with Mouse Assistant 6). Depending on the application/site, I have to click and hold on the slide bar and use the scroll ball to go up or down. But SOMETIMES, I have to click below the slide bar continuously to go up or down. It's a real pain to have to try one and the other when the first one doesn't work. Advice?

Thanks!!

[Re-Titled by Moderator]