How good are RCL guns in comparison with conventional re. accuracy? That is, if I have comparable guns, conventional and RR, with similar muzzle velocity, is conventional significantly more accurate or is it on par? Now thinking "standard" RCL round, I guess those with rocket in-flight booster will be significantl less accurate due to rocket motor.

Most RCL guns have a rather low muzzle velocity, that makes comparison difficult because many of the comparable traditional guns are pre-WW2 infantry guns of about 70-76mm calibre only.

82mm M-59A (CSFR) and 90mm Pvpj 1110 (Sweden) were some of the very few RCL guns with normal MV (700+m/sec).

True about the MV... Maybe best analogs would be German 7.5cm IG and 7.5cm LG-40, AFAIK these weapons used even the same shell, IG got MV of some 260 mps, LG-40 350 mps, ie both rather small. Are there any possible comparative trials?

Pvpj 1110 had an effective range (with HEAT shell) of 800 m against moving targets and 900 m against stationary targets. I have no idea how this compares to other nations RCLs.

The problem is that "accuracy" encompasses many things. Most recoilless weapons have thinner and hence less stiff barrels. They also tend to have less robust mounts. They tend to be very dependent on ammunition quality -- imbalances in burning rates create small but unperdictable recoil -- and the ammunition tends to degrade quickly due to exposure of propellant. All of these things need not be true, but in practice they are.

In theory, a round from a recoilless gun or conventional gun will fly the same way once it leaves the barrel. In practice, recoilless weapons and ammo are not manufactured to the kind of tolerances to give them tight dispersions. Recoilless weapons are used because of their light weight and low cost, but light weight and low cost are often the enemy of consistent and accurate shooting.