You have not indicated what scale you are working in, assuming 500mm to 1 metre....
Last question first: I have used Micro Magic turning blocks - sensibly priced and they work fine. Made of plastic, very strong, Costs about $7 for two
https://www.radioyachtsuppliesaustralia.com/products/Micro-Magic-Turning-Blocks%2C-Fit-to-Servo-Sheet-Arm.--Part-%23-M%252d2418..htmlAlternative is PeKaBe - great stuff but expensive - costs around $15 for a simple block
For an on-deck endless loop winch example - the Hurricane 1000 (1 metre) has a drum servo mounted through the deck well aft, winch is about under the end of the mainsail boom (bermuda rig). The loop runs forward to a pulley at the bow. Sheets attach to the loop in appropriate places. Easily provides sheet travel of up to 300mm
Picture below shows winch drum and mainsail fairlead. (Bow is to left of picture) Red circle was from another discussion relating to sheet adjustment methods.
The knot on the port side of the loop is where the jib sheet attaches - this the runs forward past the mast to the jib fairlead. Mainsail sheet attaches on starboard side of loop, runs aft to mainsail fairlead just in front of winch drum. Simple, strong, trouble free. Servo is EXI B1226 or similar - there are a lot of similar ones about - cost is around $30. Minimize deck furniture to avoid sheet tangles.
It is also possible to do endless loop below deck and bring sheets up through fairleads, depends on hatch position..... if you provide a bit more information, may be able to help more....