I don't recall seeing any legal info relating to speed limits on bike paths but I'll poke around and see what I can find.
I ride my electric bicycles on bike paths all over my area and to be honest I've never seen a speed limit sign. I usually keep my speed down to 10-15mph even when no one is around and when I roll up on a group of people I'll slow to a crawl, make sure they see me pedaling and give a polite greeting as I pass by.
Class 1 & 2 Electric Bicycles (eBikes) are allowed to operate on bike paths where Class 3 is generally not allowed unless local ordinance permits. Class 3 eBikes are required to have the motor stop assisting once the speed reaches 28mph, however like Class 1 & 2 there is no limit on maximum speed attained by pedaling and gravity. Motorized bicycles (mopeds), gas or electric, are also not allowed on bike paths.
21207.5. (a) Notwithstanding Sections 21207 and 23127 of this code, or any other law, a motorized bicycle or class 3 electric bicycle shall not be operated on a bicycle path or trail, bikeway, bicycle lane established pursuant to Section 21207, equestrian trail, or hiking or recreational trail, unless it is within or adjacent to a roadway or unless the local authority or the governing body of a public agency having jurisdiction over the path or trail permits, by ordinance, that operation.
(b) The local authority or governing body of a public agency having jurisdiction over a bicycle path or trail, equestrian trail, or hiking or recreational trail, may prohibit, by ordinance, the operation of a class 1 or class 2 electric bicycle on that path or trail.
Funny you should mention the Monday M1. I've been following it from the beginning back when they were Bolt. It's a great product but I have to laugh at how they claim eBike status here in California. They designed around a 5500 watt 40 mph setup then added a limiting switch (econo mode) to drop the power and speed back down to fit the Class 2 (20 mph assist) ebike law. The reason I get a chuckle out of this is I designed my first ebike the same way, 6000W 40mph with a 3 speed rocker switch on the bars. Of course I had to make the necessary modifications when the new law went into effect. The 1000w label on my motor was replaced with a 750w label and the 3 speed switch moved from the handebar to under the seat.
Link to the Monday M1 for anyone interested:
https://mondaymotorbikes.com/
Like you said not much evolution happening on the gas bike side other than 4 stroke kits. 4 stokes tend to fly under the radar better due to their lower noise levels and lack of smoke trailing from the exhaust. Still gas bikes are generally frowned on while electric bikes give that warm fuzzy saving the earth feeling and are welcomed with open arms by all, including law enforcement.
If you live in Cali and can afford to go electric I strongly reccomend it. For starters the driver license and proof of insurance problems experianced with operating a gas bike instantly become a non issue. Riding electric opens up new areas to ride, trails, bike paths etc. And for those of us that like to push the limit and operate in those grey areas it's much easier to do on an electric then gas. Law enforcement is much more receptive to electric as well as much less knowledgable to the laws and how they apply to your bike should you get pulled over and questioned.
Link below to a good read on why law enforcement tend to leave eBikes alone. Funny the article mentions Motoped which just happend to be what I used for my first electric conversion.
https://electricbike-blog.com/2017/05/16/silence-infidel-the-real-reason-police-ignore-ebikes/