Speaking for myself, the thing about the start-up orders, and any tricks learned along the way to get these FW-1884/1082 (and I imagine the FW rack unit too), is that what has worked reliably for a period of time, ends up not working reliably anymore. At one time, I couldn't get my FW unit connected at all, the the SoftLCD applet when brought up 1st, would connect to Tascam every time, when not brought up, no connection, brought up & then connection. This seemed to be something that could 100% recreate whether this worked, or not worked. Then one day that stopped doing the trick (though I still do it anyway). Some things you just do because they worked before, like the warm-up period, which was also something that could reliably recreate as a method that made a difference. Same with the power on order method.
The 'current' method that seems to be working for me is...
a) Power on/warm up the Tascam for a while
b) boot up PC, wait til Tascam firewire light comes/stays on
c) Open SoftLCD applet
d) Open my DAW sofware (Cubase) & my project.
NOTE; 'If' my Tascams FW light doesn't 'stay' on (it always comes on briefly if nothing else) after booting up PC, I will NOT open up Cubase yet! I've NEVER been able to get my Tascam working 'after' Cubase is already open! However, if my firewire light doesn't stay on after booting PC, I CAN shut off my Tascam, and then turn it 'back' on, while the PC is already on, and the firewire light will then stay on. THEN I'll boot up Cubase.
Regarding the "legacy firewire" option, though I DO use 'legacy', this is something that has not made any difference for me when I tried, whether I used legacy or not. I DO have a Texas Instruments chip on my current DAW PC, a Lenovo ThinkStation D-20, it's a built-in firwire port (no add-on card).
Regarding the Texas Instruments chip, this is something in my experience that has at least seemingly made a difference, but can only compare between 2 PC's... my older self-built Win XP DAW PC (no TI chip) which I couldn't get my Tascam to ever work reliably on them, and my Lenovo ThinkStation (has a TI) chip).
Bottom line, if I was to give advice to a new Tascam FW user, I'd say take all these suggestions that work for others seriously yes, but don't hold your breath they'll work every time forever. As for myself, I've had to change my methods.. which is very strange, and may actually indicate other things at play.
I'm using Win 7 64 bit Pro now, but if I do get a Win 10 PC in the future, I'll personally start with using the Win backwards compatibility mode, and make sure I have a TI chip in my firewire (just in case) before going any further. I may even use another Levovo ThinkStation with Win 10 since I've had a good experience with my Tascam FW-1884 & FW-1802.