Jay says:

You can run two systems, I do. It is complicated though. Most DCC locos can run on DC, but you don’t get the full benefit of DCC in doing so, that is: Being able to control each loco independently, working some of the sounds, consisting loco’s together, etc. I have too many locos to make them all DCC, some have a PFM sound in them, not compatible with DCC at all. I made a switch/selector box to select between DC and DCC and PFM, using DPDT switches. DCC decoders are pretty cheap these days, so you can convert your locos to DCC fairly cheaply. However, adding sound and DCC, costs more, and if more difficult to do, having to make room for speakers etc. As for wiring your layout: I suggest that you use block wiring, because it works best for running DCC and DC, makes trouble shooting problems easier. Also, I like to turn off blocks so that I don’t have so many locos powered up while just sitting there (making DCC sounds), while focusing on other trains.

Now, for your layout design: Along the wall is what I have done, and I like it. It does limit you as to having any figure 8 type layout plans etc. What I like about the “along the wall” layout is, that mine is only 24″ deep, and it is easy to work on. If you make one big table in the center of your garage, it gets hard to reach into the center areas unless you incorporate lift-out sections that you can work inside of. An along the wall layout can be made with modules, that can be taken apart and moved. The big table type, is too hard to move unless you can build it in sections. If you ever have to move from your house, then how do you take your layout with you to a new location? You have to decide what works for you, but as for me, I would not build a large table unless it could come apart in sections. For a continuous along the wall layout, you may have to have one or more lifting sections for entry and exit, that can be tricky too, you can find articles on how to make them.

R. Olivarez says:

I agree with Eric about not combing DC with DCC. It would be a hassle that I would not want to deal with. Either go with DC or the preferred DCC set-up. If you must have the two on the same layout, DO NOT inter-connect the two. Keep them isolated from each other, physically and electrically.

As for if you should have a room-centered layout or around the wall layout. I suggest that you do around the wall layout. That way you can use the center area for other things like working on a car, a bike, assembling something for your spouse or for constructing modules to add to your layout. If you do the around the wall layout, do it in modular sections to the standards of your local model train club. That way you can take a particular module to the club’s meetings for help or to add to their train show exhibits, when they ask for volunteers and sections for their display.