Well, when trying to condense a number of decades of Motor Torpedo boat use into a few paragraphs a lot of generalities are going to be made that exceptions to can be found.
It took a lot of years and a lot of back and forth to to suit equipment to tactics and tactics back to available equipment and please remember that the Germans, British and Italians all had sizable MTB forces in WW I (sizable in dozens anyway).
Between wars the class/type was allowed to lapse or fall to the bottom of the list of priorities in many Navies. The hulls and engines were short lived making them uneconomical in peace time and they had very limited peace time application.
The vast majority of MTBs in every country but Germany in between the wars or during WW II used engines derived from aircraft engines. Many had no mufflers or silencers which made creeping up on targets (or even holding station while waiting for the enemy to approach) rather problematic ( at least early in the war) . Some MAS boats and some pre-war/early war British boats had small auxiliary engines fitted (with mufflers) for slow speed approaches and maneuvering in harbor on the wing shafts of three engine boats.
The US sometimes fitted mufflers to the center engine (I believe, could be wrong) while the outer engines were un-muffled (center engine had exhaust cutouts for full power). Later British boats had mufflers suitable for slow speed running.
Many of these boats required the main engines to be shut down while waiting in ambush, with attendant drift problems,not to mention starting cold engines with the enemy not only in sight but probably rather angry if a torpedo has hit a ship.
Some of these boats had a rather high minimum speed, WIki says 18kts for the Russian boat/s. With a top speed of over 50kts and a rather limited rpm range for the engine (2000rpm or less at full speed?) even at idle the boats were moving at a fair clip.
Firing torpedoes from tubes wasn't exactly stealth either as
most tubes used either a black powder or smokeless powder propelling charge. I believe during WW II work was put into a
flashless propelling charge. The very light boats would have had trouble carrying the weight of torpedo tubes which are much more than a protective covering for the torpedo but actually sort of a very low velocity gun firing a 1600-2600lb projectile.
The Russian boats
seem to be an evolution of the British 55ft WW I boats. While
ALL of these boats were small compared to even a Flower class corvette there was a tremendous difference between the boats themselves. A series 10 Russian boat was 16.62 metric tons. a British WW I 55 footer was about 11 tons. the Pre-war 60 footer was about 18 tons on trials and about 20-22 tons in service. the later 70ft an up boats could go from 36 tons to 46 tons depending model and armament fit. German S boats could go 100-120 tons and the Fairmile D could also go around 120 tons with late war armament.
Obviously the capabilities of a 120 ton boat are in a whole different catagory to a 11-16 ton boat.
AS far as offense and defense goes. In the Late 30s the first flotilla of the 60ft boats was sent on their own keels to Malta, however they stopped at Brest, Corunna and Lisbon on the way to Gibraltar. Without the Germans taking over the low countries and France the need, on both sides, for coastal forces would have been much reduced as the transit times to and from the reduced operational areas would put a sever damper on things (240-250 miles from Great Yarmouth to the mouth of the EMS river. Border of Holland and Germany)
A Flotilla of Packard powered boats could use as much fuel as a squadron of 4 engine bombers in a night so logistic support was needed for any real amount of offensive operations on a continuing basis.
Again, a lot of generalities but what was the ideal situation/tactical solution was often very different from what the equipment would actually allow.