Schwalbe Marathon Supremes have thin tread. You could try them in 35mm. My last one lasted me about 3500km before something damaged the sidewall. Plenty of tread left. I wasn't that impressed.

Regarding fender clogs: you can have all the space in the world, when you roll over the correct type of semi dry mud, your fenders will clog. Riding through water, or even wet mud, will dislodge the dry mud.