How funny, you sound like me a year ago. I was in the exact same boat, re-discovering my old sets and wanting to piece them back together and sell them. My goal was also always to keep profits and put them back into Lego (whether it is for personal builds / or more investment sets). So far it has worked out quite nicely. I've definitely managed to keep these funds as separate play money for Lego and I like that aspect a lot.
I ALSO went deep with used lots, and I would agree with you that option 2 sounds more exciting. You will find people on here though that HATE buying used lots and sorting them out for resale... and they have a valid point. It is tiring and can take a lot of time.
Fast forward to me a year (and a half) later, I still have used lots to go through that I bought when I started. Don't get me wrong, I don't regret the purchases and there is still a lot of profit to be made... but they are slightly daunting to tackle. So keep that in mind when going the route of used lego... There will ALWAYS be another used lot you think is worth something and it takes discipline to pace yourself. It can add up quick and then finding the time to sort through it all can feel intimidating.
I do a little bit of both currently, hit up the clearance sales and pick up sealed sets to sit on, and then I have my used lots to still piece out. I still love to inventory, sorting, building, taking good photos, and selling these used sets so I am content right now.... but it does take some serious patience at times, so I understand people who dread it.
Advice would be, option 2 sounds more exciting to me and seems like thats where you are gravitating towards anyways..... just pace yourself haha.