Hi jazzguy!
I totally agree about the "meeting cool people" part of this!
I haven't ventured into mega-atty or mega-cart land yet, so I can't tell you anything about those.
I use Fluval (water polishing pad) to stuff my carts. I found a quick and easy way that works good for me, so I've stuck with it for now.
I tried the mod with the pen-spring... I didn't find a huge benefit.
I was using the straw-mod for a bit, it worked and gave me a good idea on how much material to put in the carts, but when I tried this Fluval, I think I finally figured out the right amount to put in the cart and I don't find a big difference with or without the straw now. So, I gave it up - the simpler the better for me.
I might try the "Blue Foam" - people seem to really like it. I just wasn't able to find it when I went looking. The next time I think of it when I'm running around, if I see any I'll get some and give it a try.
I can get a good 12 -15 drops into my cart and I'm topping off a lot less now than I was with the standard 510. I have no idea why

but I'm getting a good -oh.. 12 or more draws before I'm topping off and I usually notice that if I push it until I actually lose taste or it starts to taste "dry and harsh" - the cartridge filler is pretty dry.
I always have an opened paper clip with me and after I refill or top-off, I just re-fluff the fluval, or push it to the side and get a couple of more drops in... poke the top a little and I'm good to go.
For on the go... you can fill as many carts as you want to carry around with you and just swap them out as needed. That is what I do when I'm out for the day or night, and especially driving.
I haven't been on the go with the Tornado yet (yay for long weekends) and I imagine that unscrewing the cone to swap carts while driving might not be the safest thing to do. When I take it out with me in the car, I'll make sure to start with a full cart, and spares and see what happens
I've never used cartos - but from what I've read, they hold more and last longer than the 510 carts. Since I started with the 510 I don't mind the fiddling or futzing with it at all. It just became part of my routine, and I rather enjoy experimenting with the cart mods.
As for total e-liquid usage, I'd say I use about 3ml a day ... sometimes more if it's been a "chain vape" day.
I think once you get going, you'll figure out a good routine. You'll have to let me know how you like the mega-atties and carts, I've been curious about them since I first read about them
