Before beginning any layout....I suggest reading
A Clean Well Lighted Place by Earnest Hemingway.
Consider this tale upon your next visit to a Train Store; where the older owner and the much younger (angry) clerk want you to buy something for your layout....Anything ....Even if it doesn't work. May you find meaning in your layout, even if your endeavors are a speck in the vast indifference of model railroad suppliers; who seem to care less if your locomotive can actually run upon the track they sell.
If I was to suggest.....and I probably shouldn't.
I could write at least three apparently very different suggestions as to Scale. Not comparing each scale to the other but simply speaking to their individual attributes. In the end, I went primarily with N Scale in an O Scale Space. To test my theories on what I might want and must have's...aka Givens and Druthers > I created an Oval Tri-Way Loop on an 8 inch shelf, around the top of the ceiling of my Bedroom consisting of N, HO and O Scale beginning on the inside with 28" Radius Kato N Scale Unitrack. The next outside oval is Kato HO and the final is Lionel O-72 Fast Track.
===> Physics doesn't scale > Those things which are equal to the same thing are equal to each other. - Euclid
Meaning? O Scale Bridges measure out very well to N Scale but require the Spacing of O Scale in order to run/operate both track with trains.
Don't skip on the Radius of your Curves, the even lay of your track, don't try to fit too much in too small a space and if you want your layout to operate...Keep your first layout simple and complete it.
I would perhaps suggest, buying a Box Car in each scale, even Z Scale.
Don't do anything with them, other than look at them and handle each one.
Then get a section of track and try putting the box car on the track.
As for DCC....Ugh!
I believe the way you lay and run your track and then hook it all up (Conductivity) has more to do with successful DCC/Sound than specifically which DCC Command System you eventually decide to purchase. Plus how well you can keep it clean.
Cause in my travels of buying defunct layouts...I have ended up with nearly a dozen different DCC Command Stations. All of them have good attributes. After testing them all on a plethora of vastly different decoders, I began to appreciate the hassle of installing LokSound Decoders and running them all on a slightly more expensive ESU ECoS System; also purchased second hand at less than half price to MSRP.
Model Railroading even the choice of the best, doesn't necessarily need to be expensive.
I have good things to say about the Digitrax Zephyr, the Bachmann Dynamis, The MRC Prodigy and the NCE Systems. That is to say, I have good things to say about Buddhism, Christianity, Judaism and several other religions; which I have also studied independently on my own. DCC Discussions can resemble Religious Discussions....Which ever you decide upon...Good Luck!
With than said...What is important to successful DCC/Sound Operations?
I believe DCC with SOUND should at least begin to consider Soldering Nearly Every Damn Connection. > Everything and Everywhere <
=== DCC information is sent in packets of information...So any glitch in your trackage/conductivity and your decoder will reset; may travel a few inches and then reset again.....Learning to appreciate 8 hour LokSound Sound Decoder installs in a Brass Locomotive versus an MRC Drop In Sound Decoder in a Kato Plastic Shell Locomotive -- aka 5 minute installation is a learning curve which has taken years to master.
This bit of wisdom has taken me nearly 58 years to understand.
Create what is a manageable Layout for your life before they lay you out....in a Clean and Well Lighted Place.
In the words of Abraham Lincoln, what ever you decide on becoming Be a good one.