Most of your problems will NOT be solved with machine set-up. Sorry, that's just wrong.
At one point in my life I had many certifications. These were required to work in power plants. My welds were xrayed, inspected, and destructive tests were mandatory.
Setting up a machine is nothing compared to what you are faced with going forward. Welding is a free form art and your biggest contribution to a poor weld will be feed rate. Period. This requires practice. Period.
As you work your way around a thin wall tube you will discover inconsistencies in the appearance of the weld bead, and you have to be good at reading the weld bead to know what works and what doesn't.
A stack of dimes is an expression that's used frequently in tig welding. That look is not required but does tell a story of a welder who has mastered feed rate. The dime look exists because the feed rate and filler input is so consistent the freeze lines are visible and evenly feed. A freeze is what happens every time you stick filler in the puddle and pull it away. The filler cools the puddle every time you stick it in.
It's easy to hold the torch at proper depth. It's easy to stick filler in a pedal consistently. You challenge will always be feed rate, or movement of that torch.
I've been to two welding schools and both schools had us do drills to practice. Simply floating a torch and moving forward is poor welding, drills build muscle memory. An example of a drill would be a "forward & back, forward & back, forward & back". 1 step forward and 1/2 of that step back.
I could write until I'm blue in the face, it won't help. You jest need to practice consistently and regularly. Like any art.
Looks like we had the same job at one time. I also welded boiler tubes building power plants for about 15 years and also a lot of repair jobs on the older power plants, paper mills, chemical plants, etc. Journeyman Boilermaker and Millwright. Also worked at a high rigger in building the power plants and power plant stacks up to 1268' and done free climbing of TV and Radio towers.