The best is either push-pull or spool gun but looks like your title may be saying they are not an option. If that is the case then a 3m (4m max) torch length with teflon or carbon/teflon liner, contact tip for Aluminium (has an A stamped after the size, eg 1.2A) and U Grooved rollers in the machine.
Keep the torch lead as straight as possible when welding as any bending may lead to the wire bird nesting back in the machine.
I have a cheap Parker 3m MB36 style gun with teflon liner and "A" tips for aluminium. The MB36 size guns can take a good 200 amps for long periods. Much over 200 amps you really should look at water cooled, or watch you don't overheat the gun.
Another thing if doing a lot is get a ceramic diffuser for the torch rather than the composite material ones. If not then you will get the diffuser breaking down due to the heat, here is one of mine starting to burn up after a short while, you can see the smoke.
Can’t comment on a spool fun but I used to have a push pull gun on my censors mig pulse unit. It ran so smoothly but was temperamental and the rollers in the head sometimes would not run at the same speed as those in the machine so would still nest up.
I now have a Kemppi Minarc 200 amp and it runs ally really well on a standard torch
My two cents worth. Francis was playing up (Fronius tps320i), it's push pull gun, so I just fitted the standard (dumb) non push pull still with steel liner, just changed the tip to 1.2mm alli, as just needed to stick some alli together. Was quite supprised that it gave no trouble. The standard gun is about 4.5m long and after some use didn't worry about keeping it so straight and it worked. Doesn't have the reach of the 8m push pull, but is lighter and more flexible. I suppose there is a big difference depending on the manufacturer as to how the equipment works. I have had more trouble with an older Binzel push pull gun than using the Fronius straight dumb gun, it also depends on how much or how hard you use it. Once I cranked up the power and put down a longer weld you could feel the wire starting to stick to the tip, which upset the feed a bit. However was just supprised how well it went overall. Just a note only use 1.2mm safra wire 5356. The thinner the wire I could see this becoming a problem.
A quality wire feed and a proper set up power source can make a huge difference. We hired a Lorch S3 to work with 1.2mm 1080 pure aluminium wire, because we were having such huge problems with a push-pull. The thing that clinched the deal for me was it demoed set up with a 4m watercooled regular torch, with a KNOT TIED IN IT, running this super soft and finnicky wire no problem at all.
It's not just the drive rolls, it's every single component that helps it work so well at this level, from simple things like the brass guide tube supporting the liner in the feeder, all the way to the top quality watercooled tip keeping things from overheating and snagging on the tip. Loads of high quality machines run 5356 and even softer 4043 wire just fine when set up ok, but would struggle running 1080. I imagine Henry's Fronius is similar
^^^ The reason I was so supprised is that the dumb gun (no electronics, just a push gun) still had the steel liner inside, all I did was change the tip. The push pull gun (air cooled ) was playing up and giving some fault on the welder display, so I tried the push gun. I don't think that problem is sorted yet, but not required to do any alli recently so don't know. I also have a water cooled push pull gun (just in case) still in it's box. It will only come out if I start doing longer runs and at higher power