It probably wouldn't have been like Britain, at least not for a while - Nicholas II was definitely "old school" as far as monarchs went and had zero desire to share power with anyone. The German Empire was closer to a constitutional monarchy than Russia was going into World War 1 and, thanks to Wilhelm II's idolization of the military, was basically a military dictatorship with a "representative" rubber-stamping committee in the Reichstag.
That said, Russia's military probably would've been in better shape going into '39 under Tsarist rule than it was under Stalin. Russia's military was undergoing a modernization program (increased mechanization, greater operational staff independence, etc.) going into World War 1 that was a few years from completion. If World War 1 started in 1917 instead of 1914, Germany wouldn't have had a poorly organized, slowly mobilizing, poorly equipped army of peasants on its eastern frontier - it would've had an impossibly large, well-equipped professional army backed by a relatively modern infrastructure (Russia was working on getting their railroads up to international spec, among other things) bearing down on it instead and Germany knew it. That's part of the reason Moltke and the rest of the German General Staff were in such a hurry to start World War 1; their window of opportunity, rather small to begin with, was closing fast. Instead of completing the modernization program, though, Russia's military was quickly chewed to shreds by the Germans (note that the Russian military, poorly run as it was,
easily handled the Austro-Hungarians without serious issue), devoured what was left of itself during the October Revolution and its aftermath, then re-adopted the grand Russian tradition of promoting officers based on political considerations instead of tactical merit under Stalin; granted, Nicholas II wasn't much better than Stalin on that front, but at least he didn't make a regular habit of killing large portions of his General Staff whenever he came down with a case of the "vapors". Similarly, Tsarist Russia's economy wouldn't have had to suffer through the pre-NEP "War Communism" economy, nor through Stalin's abandonment of the NEP and the Holomodor. Of course, some of the resulting gains would've undoubtedly been lost in the Great Depression, but millions of displaced Ukrainian peasants probably wouldn't have starved.
Long story short, Nicholas II's "divine" leadership would almost certainly have been no
worse for Russia and its military than Stalin's leadership ultimately proved to be.
Also, the "tanks on horseback" bit is actually a magnificent bit of
Nazi propaganda - like most militaries of the time, horses were used for reconnaissance and scouting. Don't forget that small, inexpensive, reliable all-terrain vehicles were a rather recent development; full scale production of the Kübelwagen didn't begin until 1940 and the Jeep didn't enter production until 1941.
