Ralph gave you the GOOD points of glow ignition
And if you understand the engines - this setup works very well
BUT- as you asked - ALL are affected.
The really negative point is that ignition occurrs when the pressure tempurature combo is "correct for combustion"
the position of the piston can be ANYWHERE.
The glow plug can even be dead.
"how so???"
alky and platinum react - alky makes the platinum glow and that creates enough additional temp for the fuel to ignite.
It is a cataylitic reaction.

Some engines will start with no initial warming of the plug - really-
IF you up the compression to gain more torque -you can easily induce a pre ignition.
also you can -as the thermal rise sets in, go straight to detonation .
So the guys who know glow-- add nitro, change compression /oil quantity/ pipe settings -on and on --to obtain proper "timing.
The best power setups we ever did , were on spark ignition, alky and nitro-
and tuned exhaust.
this setup had perfect table manners - instant starting- extremely smooth ,low idle - flawless transition and more top end than same engine /pipe on glow only would do.
Why?
the timing was controlled .
On a flat out full bore racing setup - you simply chuck everything in favor of best WOT performance
so once you balance compression (including exhaust setup) -- you are only left with possible runaway temp - which causes some real problems .
My newest ignition setups have a tattletale tach - so I can see how fast I am really turning in the air .
so far I have not used it for max power tuning -just been too durn busy.

thirty years ago --we used an audio tach- to read in air rpm - it works if you know how to use it.
basically it was an audio pitch calibrated to scale - - you listened and tried to shift the audio till it matched the sound of the engine in the air
under ideal conditions you could get very close readings
This is the same kind of setup -50 years ago we used to calibrate our clarinets- really--
it was called a stroboscope - and you matched each tone on the instrument with a calibrated signal and watched a spinning wheel lamp, appear to slow and become stationary - meaning you were synchronized.
Bottom line - yeh you can use glow on gas engines -but it is NOT a plug and play setup