I was in your situ a few months ago. I put some distros on USB sticks, decided which one was more to my liking (Ubuntu) and then went for the full install a week into it. There were unexpected unpleasant surprises, namely i had to repartition my ssd drive (and reinstall Ubuntu), and i ran into some issues with read/write permissions for USB sticks. Try distros and install on your old laptop like you said. Test drive it to your satisfaction
I was in your situ a few months ago. I put some distros on USB sticks, decided which one was more to my liking (Ubuntu) and then went for the full install a week into it. There were unexpected unpleasant surprises, namely i had to repartition my ssd drive (and reinstall Ubuntu), and i ran into some issues with read/write permissions for USB sticks. Try distros and install on your old laptop like you said. Test drive it to your satisfaction