The usual first thought about strategic quick reaction forces is nowadays about American-style gold plating: Air-deployable forces that fit into gold-plated transport aircraft and deploy within days. This fits to a country that need little military because it has no threats on its own or a connected continent and meddles primarily on distant continents. It's obviously unsuited to the defence of Europe, save for quickly deploying defences for some Mediterranean islands.
The quickest administrative march within a few thousand kilometres with no early notice is nowadays the road march with wheeled vehicles that approach the cruise speed and reliability of commercial heavy lorries.
Tracked vehicles should march long distances on a flatbed waggon or on a dedicated flatbed semi-trailer. It takes time to load and unload the train, but repairs of broken-down vehicles and worn parts tend to take even longer. The train itself can travel quicker than lorries on motorways, but loading and unloading are important fixed (time) costs and the railway network is much more susceptible to sabotage and attack than the road network.
In the end, it's reasonable to expect most if not all tracked vehicles to arrive later than the wheeled vehicles for a deployment such as from Germany to Lithuania, for example.
Doctrine and force developers did not yet create any truly optimised answer to this two times of arrival problem.
Example: The German Division Eingreifkräfte has two manoeuvre brigades; a Panzerbrigade and a Panzergrenadierbrigade - the latter is identical to the first except no Panzerbataillon (no MBTs). These brigades would be ready for employment only once at least one brigade and much of the division's support troops arrived.
A different approach that would allow for a quicker readiness for action at the Polish-Lithuanian border would consist of one component capable of a very quick road march with no early notice (wheeled vehicles and few tracked vehicles on wheeled semi-trailers) and another component meant for deployment by rail* if the march distance exceeds about 500 km.
The "'wheeled' component would need to have limited combat readiness at least - for defensive actions and infantry-based offensive actions in cluttered terrain. A brigade with two infantry battalions could have one equipped with armoured combat vehicles (such as APCs, HAPCs, even if need be IFVs) yet still deploy it at first with lorries. The other could use wheeled all wheel drive APCs. The result would be two infantry battalions and the brigade's artillery (possibly tracked SPGs hauled on semi-trailers) available for action before the bulk of tracked vehicles arrive. Thee would be hardly any downside to this in case of a timely deployment of the whole brigade, since the only requirement would be a few dozen more lorries including about 18 70 ton semi-trailer lorries.
The bigger problem for the gain of maybe one or two days in face of disrupted rail traffic would be the doctrine side: The brigade would need to know two doctrines; one with tracked armoured combat vehicles and one without them (with a smaller tactical repertoire). These two should be mastered anyway, though: One can expect the AFVs to dwindle away during days or weeks of action, with little or no replacements arriving. The infantry may (will) melt away as well, so the brigade should know a mode of operation in which the duel (line-of-sight) forces provide little more than pickets and the (hopefully survivable) artillery keeps hammering while evading line-of-sight contacts.
I wrote about strategic QRF here because I'm convinced that the rapidity, not the size, of forces is the key metric for deterrence value against a Russian coup de main in the Baltic and such a coup de main is the only plausible scenario for collective deterrence and defence in Europe today. All other collective deterrence and defence scenarios would be negligible in either probability (nuclear war etc.) or scope (such as the irritations at the Turkish-Syrian border).
Years if not decades have been spent elaborating about quick deployment forces and professional journals have published hundreds of articles about airlift of combat vehicles, but none of this was of great relevance to the only truly noble purpose of European military power: Deterrence and defence or collective security in Europe.
*: The Deutsche Bahn has according to itself 1,628 diesel locomotives. Electrical power locomotives would be too vulnerable to electrical supply disruptions for the QRF's deployment..