As to being the fastest? Yes, but with training.. The design of the SMLE allows one to throw the bolt without removing it from one's shoulder, and to maintain a sight picture..
Also, consider it's 10 round capacity.. If you have extra mags loaded, it is not that hard to maintain a rate of fire rivalling many self loaders..
Quality is very subjective when dealing with the SMLEs.. Some of the early No1MkIII's were beautifully made, in comparison to the later No1MkIII*, which was a WWI modification..
The No4MkII is basically a No4MkI with an action mounted trigger, as opposed to the No4MkI's triggerguard mounting.. It's fit, and finish in my experience is no worse, or better than equivalent No4MkI/No4MkI* rifles.
Availability has been scarce in my experience, compared to the hoardes of No4MkI's, although when you find one, they are beautiful, and usually new/unfired.
Recoil is subjective.. I find Enfields very plesant, but I do not shoot off of a bench.. The No 5 is a bit harsher than the No4, but not that bad that you should pass one up..
Consider buying two, and fitting one with the fine Parker Hale match sight..Makes the old "smelly" damn fun to shoot.
Meplat-