My thoughts...
Note, that is IMHO.
Both vulnerabilities theoretically allow a program running on your computer access any data in memory of your computer. So to have ANY impact, your computer should RUN that "bad" program. That can be:
a) JavaScript in your browser. So
your Browser MUST BE PATCHED NOW. Probably there is some performance penalty, but note that JavaScript IS NOT a binary code. So I guess that penalty is minimal if at all noticeable. That should make your computer SAFE for Meldown and Spectre (if browser developer do this right... but if they do not, you can be attacked by 1000+ other vulnerabilities, so nothing new here).
b) since I guess you are not allow arbitrary people run arbitrary programs on YOUR computer (if you do, you can have more problems then just with meltdown), if the bad program is there, you already have a virus. Not good, but nothing new (any virus can read all your data in any case). The situation is SIGNIFICANTLY DIFFERENT for computer resources providers like cloud services, web hosters, etc. They ALLOW many people run ARBITRARY programs. I repeat, on a private computer, (b) is NOT a problem at all. But IF YOU ARE A VOLUNTEER in scientific calculations (f.e. BOINC), I recommend to TEMPORARILY STOP that activity till the situation is clarified.
So, for a DAW computer... Not installing OS patches (or disabling them) does not make your computer less secure. But I repeat, if your computer is connected to the Internet, patches for Browser is A MUST.
Well. MS and other OS providers do not want to go into details. So they give you patches even if you can not profit from them (as collecting telemetry and running other useless for you tasks). So lets think which impact such patches can have on a DAW.
The "brick wall" is applied on process switches. So when the program asks OS for some activity:
* audio/midi recording is a tiny operation for modern systems. Even if that is "slowed down" by a factor of 10, you probably will not notice (have you seen any difference in RECORDING to PCIe SSD vs SATA SSD vs HDD?)
* loading huge sample libraries can be hit, especially from PCIe SSDs.
* Audio I/O theoretically can be hit. But that is FIXED SPEED operation (unlike loading samples, it make no sense to "send music faster". So, if there is some impact, for the system in general it has absolute upper limit. I do not think that can be noticed.
The "heavy job" is done within plug-ins. They are running inside the DAW (till bridged 32bit in 64 DAW...). So like games, most critical for a DAW operations are not affected.