The plumbing codes today require that in new construction or remodel, an anti-scald type of valve be used. MOST but NOT ALL of these are single handle types. You can find from Delta and others a set up that has the two ( or 3) handle function. One handle is on/off/volume and the other handle is temp control, and this has pressure-balanced or thermostatic scald control.
Your "faucet store" guy does not know his product lines very well. Ask him to get out the catalogs and have a look.