I wish there were a more accurate point of referance I could turn to. I went for an oil with teflon, and it tends to be a notch or two smoother than grease in my experience, but of course not under all circumstances. I tested grease on the worm gear, but landed on the oil I use the most (Finish Lince Ceramic Wet Lube, it's very good, and what I can easily get here). If you had oiled it well I doubt there's much to gain from fiddeling about with lubricants. The manual says something like "oil before every time you use it, and not after" LOL
. I have been very happy with my Supermatic after I replaced the old rubber friction wheel with a new one and got the correct bobbins for it. I couldn't order from Ray White, so I ended up with a aluminium pulley with O-rings.
Maybe it's about getting used to the sound, it's a different than other machines, but withing reasonable noise level. I'm used to a Singer 99, a 201, and an older Bernina, a couple of new Janomes, I test sew various new models now and then. The Supermatic feels sturdy and very capable when I use it. I had to find new felt feet for under the base when I first fixed up my Supermatic, they were missing. I'm not sure what the original feet were, maybe some type of rubber. I used sturdy furniture felt and it works well. A sturdy table and sorting out some type of cushioning feet under a machine can improve noise levels a lot. Don't worry about running the machine, it's sturdy and are they are made to work. I wham mine on full speed regularly (at least for some zigzag jobs and a few of the cams). For the most part I tend to use straight stitch, and I tend to sew slowly when hemming and joining pieces.