The main reason I got the 2600+: Medieval Mayhem/Warlords/Kaboom on the big HDMI screen. I opened up a set of new old-stock paddles to try it out.
Kaboom was the first game I plugged in: the buckets were mega jittery and the latency was untenable - aka not zippy. Guessing there's a 150ms/200ms delay here. Now, Kaboom is known for its slightly jittery control on OG hardware, but this is at a whole other level. Couldn't make it past the 4th level.
Used the same paddles on my OG heavy sixer and my modded 7800/w Retrotink. The typical tiny amount of Kaboom jitter was there, Got my usual level 8/3k plus score on each with no problem, though you could feel the Retrotink/HDMI latency a bit.
Warlords had no jitter at all, but definitely see the same latency issues as Kaboom. The latency, on a big screen, forces me to overcorrect as the paddle isn't where I expect it to be for a fraction of a second.