If any piece of this setup was bought with anything but cash (or is in some way traceable to you - e.g. you use an old smartphone you own), then you may be leaking some data that would allow identifying you (phone IMEI and MAC notably).
As other have pointed out, location is in all cases recordable (and very, very, very likely is being recorded). As would be the location of your current cellphone if you have one.
Consider, too, that unless you make a point of disabling your tethering phone (e.g. remove battery, SIM) after each use, there may already be a link to your home, etc.
In conjunction with a fair bit of other opsec, this could be reasonably effective, and to a point, how well the efforts protect you might also depend on what you are using all this for.
Finally, consider that if you do USB tethering, then if you had very serious adversaries, you might be opening yourself to certain forms of compromise.