In europe the 190E came with several engine-types of which most were not available in the US.
I think the Us have the 4 cylinder: 2.3E 8v, 2.3E 16v and 6 cylinder 2.6E 12v.
Additional to those engines we had also the 1.8E, 2.0E, 2.0(not E). All these were 4 cylinder 8 valves.
The 190 is a very reliable car (as long as it is serviced well) and is able to last a lot of miles. I had a 190 2.0 Diesel and drove it up to 600k km without any expensive repairs!
The 2.3 or 2.6 will both do well...and NO, the engine does not require valve adjustments; it has hydraulic "rocker arms" or however they are called.
Valve seals, however, need to be renewed occasionally cause they tend to get hard after some time/miles which will cause some oil-consumption.
with a minor 600+k