Two quick things to add. All points so far have been valid, but here's another view:

121 experience is important. It's a different world, and time in the seat is the only way to get it. Regional is the way to get that.

This in mind.... I found the best way to do the regional thing was to go in with a good background in IFR ops, built through Part 135 flying and being a 135 instructor pilot. I was able to then go into a regional as a direct entry captain for the turbine time. Got my PIC time in a 121 crew environment, and then... well, then I went to Alaska and now fly Beavers on floats 'cuz it's serious fun. But when I want to go to an airline, I now have the boxes all checked.

I've never been a copilot. It just sorta worked out that way. Going from part 91 into 135 allowed me to build all the skills as PIC in singles, twins and IFR stuff. But this doesn't teach how to play well with others in a crew environment. It was important to get that experience, and the only way I could get that was through a 121 regional. It just worked really well for me. Maybe consider looking for a hardworking 135 that will put you in a twin, flying challenging IFR. It's some of the hardest, challenging and IMHO, best experience a pilot can find. Then take your 2,000 hrs PIC to a regional hiring direct entry captains, and pick up that PIC turbine type rating! Another 1,000 of 121 PIC, and you can do whatever turns you on. Maybe after you get a look at the regional and 121 world, you'll go to Alaska, too!

Good luck! Hope you find your path.

Ronin