Is there a way to have both ssds plugged into the pc at once to use macrium reflex?
If you use Macrium Reflect to clone or image, you would leave both drives connected.
If you do a clean install you DEFINITELY should not.
What should you do?
I'm guessing you have never used Macrium and have never done a clean install.
How long would it take you to do a clean install and then reinstall all your applications? Say that is X hours.
How long would it take you to learn how to use Macrium and then use it to clone or image to the new drive? Say that is Y hours.
Is X more or less than Y?
That's unknown, depending on your skill level, ability to follow possibly shaky instructions, tolerance for frustration, and some more stuff we don't know.
You might spend 10 hours fiddling with Macrium and wish you had done a clean install. If experienced with Macrium, you could have the whole thing done in an hour or so. Everything just like before, but on a new drive.
You might spend 10 hours fiddling with a clean install and wish you had used Macrium.
Knowing no more than you've said, I'd probably direct you to a clean install. Everyone should know how to do a clean install and do it at least once.
You should learn Macrium as a backup tool, but maybe simpler for you to do a clean install for your immediate problem.