Oil boilers don't usually have much modulation range, which tends to make them less refined...
I was reasonably impressed with the Ideal 35kW combi that I had at the other place. It kept a small store of a few litres of water tempered ready for use. So you could demand a very slow delivery and get hot water, and the boiler would fire intermittently to recharge the depleting store. You got some temperature variations as it was doing that, but not dramatic. As you ramped up demand it matched it with its modulation capability until it ran out of puff at about 15 lpm and the temp would start to drop off. The cold main in that place could only manage about 18 anyway.Pretty sure the WBs have a similar capability as do the Vaillants. (although you can turn off the pre-tempering if you want on those)
I fitted a 24kW Vaillant for a friend - just for kitchen and a single shower. That was also quite well behaved for the application.
My current system boiler / unvented cylinder is obviously "better" but some combi systems can be OK IME given then right circumstances.