I used TP from 3.0 to 7.0 and a little bit of Delphi 1, and contemporary Turbo C; I dropped to assembly often, dropped TP bound checking often, and was well aware of all these controls.
Parsing with a *ptr++ in TC was not matched by TP until IIRC v7; 16 bit watcom often produced way better code than either TP or TC.
And, as you say, indeed when speed was really needed, you dropped to assembly; no compiler at the time would properly generate “lodsb” inside a loop, although watcom did in its late win3 target days IIRC.
I cannot say I ever bother to benchmark parsing algorithms across languages in MS-DOS, so maybe that was a case where Turbo C might have won a couple of micro-benchmarks.
That was just an example. In general, properly written TP code (properly configured) was on par with properly written TC code, and both were slower than properly written Watcom code in my experience - I did them all and switched frequently.
Parsing was one example where C shone above Pascal, and there were others. My experience was Watcom was consistently better, but in general C was sometimes easier/faster, Pascal was rarely easier/faster, and if speed mattered ASM was the only way.
Well, as I mentioned in several comments, in what concerns my part of the world, in a time and age where a BBS was the best we could get for going online, Watcom did not even exist on my radar until MS-DOS 32bit extenders were relevant.
So we are forgetting here the complete 8 bit generation, and 3/4 of MS-DOS lifetime.
Parsing with a *ptr++ in TC was not matched by TP until IIRC v7; 16 bit watcom often produced way better code than either TP or TC.
And, as you say, indeed when speed was really needed, you dropped to assembly; no compiler at the time would properly generate “lodsb” inside a loop, although watcom did in its late win3 target days IIRC.