Basically cartos can be pretty "finicky". My experience has been that while some 808 cartos work fine on the Infinity as-is, I have had 100% success by using a 901/808 adapter on it (901 is the same threading as 808). 808 cartos are widely available, decent prices. Alternately a 901/510 adapter would let you use any 510 cartos -- a 901/510 runs about $2 - $3, available at many places (good prophets, liberty flights [I believe], Ikenvape,...).
901 atomizers should work, though I never used them. Infinity I only used with cartos -- didn't try atomizers until the last few months.
Carto tanks are really simple, fairly short learning curve, great if you have an eliquid that you like a lot, cuts down on refills. I haven't used the Smoketech tank, but the seals felt solid when I was checking carto fit, which means they won't leak, and the polypropylene plastic is highly resistant to cracking (some cinnamons, menthols, acidic fruits crack many standard clear tanks).
The 801 fusion cartomizers from Ikenvape, 2.5 ohms, are just a really nice carto, handle a lot of eliquids well. They are the only ones I use regularly now, though some people prefer the boge cartos (2.5 - 3.4 ohms is the sweet zone on the Infinity for resistance, in my opinion; I vape mainly 8 - 10 watts, which would be running at 4.5 - 5V. Infinity doesn't have voltage markings, you just rotate the dial to get what you think is good flavor, then leave it there until you feel like a change. If you overshoot, too high a voltage, no harm, the PV will just cut out until you decrease it slightly.)
The package shows as departed Syracuse yesterday, so it should be there fairly fast