I switched to propylene for cutting and use with a rosebud. The acetylene can only come out of the acetone just so fast, so you can often have plenty of acetylene yet cannot get sufficient flow to decently use a rosebud. It seems like the tank is not full, but it is just a matter of how fast...
For TIG welding, I use a standard #8 lens and switch to an auto-darkening for MIG and stick welding. The #8 setting seems to work well on that as well. You might want to look into putting a 1.5x magnifier in your helmet if you are not wearing reading glasses while welding if you wear bifocals...