i'm not familiar with the brand, but the cpu is decent, the graphics can help, but some front ends like centrafuse don't use graphics cards last i heard, so depending on the front end, it won't help--not a big deal, but something to keep in mind. back to the board--most of the reviews i've seen rate it like a mid-grade economy car-- it's good for normal transportation, but just don't expect to be doing on-the-fly video editing, etc..
instead, i recommend the m1, or m3-- both are a similar form factor as the pico psu, or the m2-- which is a lot bigger, but i've seen everything from a similar atom/fusion cpu setup all the way to i3 setups using one without issue.
for the most part, that cpu is pretty low power, so i believe the m1 or m3 should be fine for the board alone, but that doesn't count any peripherals you might add. so before ordering, i'd recommend trying to nail down how you expect to use it, and what kind devices are going to need power.
there are a lot of different power calculators online-- i can't seem to find the one i liked before, but there are some out there that will give you a good estimate for how much power the system will realistically consume.
a lot of guys mount the wifi antenna's somewhere around the rear window, so your options for that are to either use a usb card, or use rp-sma extension cables.
extension cables will have a lot of loss, so the mounting a usb dongle up there will be best in terms of signal strength.
this is my experience with this issue:
as for as installing a optical drive, it's completely personal preference. i've got one, and though i rarely use it, it comes in really handy for the days that i buy a new cd, and want to listen to it on the ride home(i no longer download music, the quality is too poor IMO, which slightly contributed to my forum name )
there are plenty of installs that are 'drive-less' and they work perfectly fine-- most of the time, you can update the system over wifi or usb anyways, so there really isn't a need for it.
as far as the megasquirt, you're not the first one to come here using it, so i believe it's completely possible, but my interests lie in lighting and audio, so i can't help you there..