Not familiar with the ACE. I have a 2015 Vegas; but that said, they are all pretty much the same system-wise. Here is a picture of my hot water heater (yours is probably pretty much the same. Look down and toward the left and you'll see a plug with a green colored X on it. That plug is the plug to drain the water heater tank.
Your water heater bypass valves should be on the opposite side of the water heater somewhere
inside your RV -- behind a panel in the hallway, or in a cabinet, or under a sofa. Maybe an ACE owner will chime in to tell you where the bypass valves are.
In 2015 I compiled an owners' manual for the Vegas/Axis. I posted a link on the forum to share with other owners. So far about 2300 people have downloaded the manual and its been viewed by over 18000 owners. Here is a link where you can download the manual. Although it's not specific to an ACE, many of your systems are the same as on the Vegas. There is a winterization checklist you might find relevant. It doesn't show the location of your bypass valves or low point drains; however, the procedures will be the same once someone helps you with the locations. Here is the link:
https://1drv.ms/b/s!AiYx6DLSeiiPgYBSfmvPhwGsR_0TkQ
You should also go to the Owners section of the Thor Motorhome website (this link:
https://www.thormotorcoach.com/owner-resource/) and put in the information to establish an account. Once you have an account you can access all the manuals there for all your systems and a list of the model numbers and serial numbers of all the components installed on your specific motorhome. At that site you can also request production drawings for your VIN from Thor. You should ask for all the drawings for the fresh water system, sewer system, and AC & DC layouts and schematics.