Just to answer a few of the questions and provide a bit of clarification:
5.8 is nice to start because the antennas are small, it's affordable, interference with other equipment (GPS/RC TX/RX) is minimal and there are goggles available (like the fatsharks) with the RX built right in. 1.2/1.3Ghz will give you better penetration but you've got larger antennas and the risk of interference with 2.4Ghz for your control link.
Head tracking is only included in higher end goggles. You're not going to find it on lower end goggles. You could always add an external head tracker just like you can always add an external RX - but then you're dealing with more wires and things to setup. The Dominators are the only Fatsharks with headtracking. The Skyzone goggles also have headtracking built in. Personally I'd rather have an external module since I haven't heard very glowing reviews of the built in setups and I suspect there will be quite a bit of advancement in head tracking soon with VR becoming more popular thanks to Occulus Rift. Having a separate external tracker means you can upgrade to something better at any time without waiting for the goggle manufacturer to update their module.
As for Fatshark Vs. Boscam for 5.8ghz. Both setups allow you to select from a number of different frequencies (though sometimes those frequencies overlap. Like the 32 channel setups that give you 32 possible frequencies - but the signal width is wider than the channel separation so you can't have 32 people all using their own channel at the same time. You'd probably get around 5-6 people before they start stepping on each others signals.) The bigger issue is that the different manufacturers use different frequencies within the same band. So while Fatshark and Boscam are both running on the 5.8ghz band they don't support the same channels within that bad. So a Boscam RX can't recieve a Fatshark TX. But at the same time the frequencies are close enough that someone using a Boscam TX could overlap onto a Fatshark channel making that channel unusable or only usable with greatly reduced range on Fatshark.
With just about any frequency selection though you'll be VERY limited on power without being licensed. Not sure where you're located but getting an amateur radio license is really all but necessary to do FPV legally in almost every country on almost any band at usable power levels.
If you want to step up to 1.2/1.3Ghz for the better penetration then there's really no point in getting goggles with built in RX since none of them have a 1.2/1.3Ghz RX option. So you'll have the deadweight of the built in 5.8 (or 2.4) module in the goggles just sitting there doing nothing and you'll be dealing with a cable to connect to a ground station.
That's why I went with the Base SD goggles. They seem to be the best bang for the buck and they're the lightest since there's no integrated RX. Since I plan on going to 1.2/1.3 at some point the built in RX didn't really appeal to me very much while the extra noise filtering and adjustable IPD on the base all for less than the cost of other headsets seemed like a no-brainer to me.
Do you consider the mobius a board cam? If not, the only reason I would choose the Mobius right now over a board cam is because it allows me to save the video locally. I really like that because I like being able to show others later and watch my flights again. I realize that some of the board cams have a much broader capability but I figure the Mobius is sound and reliable for a beginner, agree?
No the mobius has as much or more delay than the gopro. Both mobius and go pro have the benefit that they can record, but neither is very well suited for FPV IMHO since they both induce a delay in the signal. Not to mention board cameras are cheap if you smash them up (and being out front they do tend to take some hits when you crash.) Even a cheap $15 board cam will have less latency than a GoPro so you're seeing what's actually happening and not what happened half a second or more ago.
I fly a board cam and am planning on picking up a mobius shortly which I'll run in parallel for recording. I'll just mount the board cam and mobius as close to each other as possible and adjust them so they have almost the same field of view. I'm used to cameras with less than 100% accurate viewfinders so composing a shot with a slightly different view than the recording cam isn't a big deal to me.