No matter what vehicle it is, urban warfare won't be good for it.
Urban warfare is the the most difficult because enemy forces can be in the building next to you and you may not realise. Also the elevation provided by buildings and structures means instead of attacking your frontal armour or even side and rear armour, they can engage your top armour... which is almost always rather weaker than from any other angle except underneath...
A guy with an rpg can pop up and fire at the vehicle in 3 seconds leaving no time to the crew to react even if they see him.
Quite true but APS systems turned on should protect the vehicle even from attacks from above... simply because new ATGMs include top attack options because the top of vehicles is a weak point in terms of armour thickness.
First gen Soviet and Russian APS systems were not ideal for top attack weapons, but I would suggest modern systems will defeat top attack munitions too.
Even a PKM will make terrible damages on the roof of many vehicles.
Many light vehicles have tops as thin as 20mm so yes, even a PKM at short range with armour piercing rounds can be effective... and even against the heaviest vehicles it can damage equipment and optics and aerials.
With new vehicle families many of the lighter vehicles like APCs with remote weapon stations the ability to fire back is actually pretty good and if you break cover and fire a PKM at a column of armour in a street even leaning back in behind the sand bags might not save you if they have audio sensors that detected where your shots came from... after firing your burst at the tanks you might find a nearby T-15 detected your burst and returns fire with a burst of 3-4 57mm high velocity cannon shells... perhaps APHE rounds that penetrate in to your sandbags and blow the room you fired from to bits...
It is very dangerous for armour, but it can become rather dangerous for enemy forces too.
I believe that one of the requirements for the armata was that the roof of the crew capsule would have to be protected with composite armour that could withstand a PG7 warhead, in addition the both the frontal hull and turret rooves have ERA.
The heaviest armour is the frontal hull armour which makes up the crew capsule... all the heaviest armour is covering the crew from all angles. The weapons... including remote weapon stations are not as well armoured but are able to elevate to return fire even in built up areas...
In chechnya the tanks were not properly supported and could easily be ambushed, in the near future Russia will have numerous teletanks like the Uran-9 to deal with troublesome neigbourhoods.
In the second conflict in Chechnia they were less gungho... less willing to barge in to urban areas... They will have robot vehicles and UAVs but they will also likely use more fire power and also more precise weapons and equipment to ensure they kill more of the rebels rather than let them escape to fight another day.
But Russia had heavy vehicle family during the war in Chechnya as well. T-90, BMP-3, BTR 90. What's the difference now ?
AFAIK they have not had the BTR-90 in operational service, the BTR-80 vehicles and BMP-1.-2, and -3 vehicles don't have especially strong upper armour... in fact they could probably be penetrated with 14.5mm HMG fire from above... like most western IFV and APC equivalents.
In combat the IFV and APCs were taken out first because their main guns could elevate and fire back at the enemy teams in the buildings... once they had been dealt with they blocked the exit for the tanks whose main guns elevate to less than 30 degrees, so they could take their time to destroy those.
A new Armata unit however means all the vehicles have MBT level armour protection so they will be much harder nuts to crack... and all will have APS systems and other equipment to make them more difficult to deal with. They will also have a range of high elevation weapons to return fire with, which makes the job of the ambusher much more dangerous... they could even use onboard lasers to mark the buildings around them and call in an artillery strike...