there’s a lot of it depends. With a bunch of accounts and a null super umbrella multiboxing rorquals is going to give a ton of income, but in highsec with a few accounts mining is going to suck. And a lot of inbetweens.
FW missions have a lot of variability depends on which tier each militia is and what systems they control. High tier you get a lot of LP, but that LP is usually pretty low value, I guess the question is what’s the overall value? I haven’t run FW missions so I can’t say. Also if you can afford to hold that LP till the tiers shift you can cash out at a much better value. Also sounds like you can decently multibox FW missions.
As for some other content:
General missions: pretty easy to multibox burners for 200-300 mil/hr per account needs ~20 mil focused SP to get going on each character and a decent investment in ships.
t4/5 abyss sounds like it’s not that hard to 3 box these with frigs. sounds like 600m-1b/hr with these. Bit less single boxing with one cruiser.
trading, 600T moves through the forge each month, a fairly small claim on that is a lot of isk.
production: again a lot of isk but also can cost a lot to get going. A lot of the value is in build components but a few percent profit margin can be pretty nice.
Personally I did a lot of burner missions and then mostly trading/production to build my wealth. Been meaning to try FW, at high tier the LP is crazy and I can afford to hold til the tiers swing. Also probably going to try 3 boxing frigate Abyssal space soon.