For me Toku's traits scream for a drafting strategy in the mid game. Drafted gunpowder units (muskets, rifles and infantry) will get the free combat 1, drill and CG1. You should run Theocracy to get drafted units with at least 2 xp (drafting halves xp for the unit) and early on that means 3 musketman per turn with pinch as well as the other free promotions... Later drafted riflemen with C1, drill, CG1 and pinch (or CG2 for defenders) are going to run over anything and massacre the counter attacks the AI throws at you after you take the first city.
So I would plan and develop a drafting economy right from the start. You need to prepare to get the best out of it and you need to research Nationhood quickly. So I'd recommend the usual drive towards Liberalism, take Nationhood as the free tech and then research Gunpowder. Then mass an army of musketmen as you research Engineering (for trebs and faster movement).
You could draft samurai (while researching Gunpowder) but they don't get the protective promotions and only cost 70 hammers anyway, whereas musketmen cost 80 and rifles 110 hammers and paying one pop (worth 37 hammers with slavery) for 70 hammers isn't quite as good a deal for me

.
The power of drafting is in the free hammers it injects into your war economy and the +2 happiness from barracks is good in all your cities anyway when you're at war. You don't have to draft in all your cities. It is better to prepare special cities that pump out most of your units. These cities don't have to be very big as the minimum size for drafting is 6. If your universal happiness cap is say 12 they get 2 drafts before they need any special attention (see later ideas

). Obviously they need a good food supply so farms are favoured over cottages.
How to maintain happiness while drafting? There is the old trick of using the Globe Theatre in high food city and draft one unit per turn (and with a good food supply also grow 1 replacement pop). That is a great long term drafting strategy but has 2 problems:
a) it is only in one city
b) it takes a lot of investment (6 theatres and building The Globe) that takes time to build.
Another trick is to use HR to maintain happiness in the city as you draft units. The unhappiness from drafting 5 units is -15 and can be countered temporarilly by keeping the drafted units in a stack and moving other military units needed for war there as well. When you go to war just move the stack out and use slavery to reduce the very unhappy city to size 2 where is doesn't cost much in maintenance. After the war just bring your big stack back and the unhappiness from slavery and drafting will have worn off enough for the city to regrow. This is a very good way to raise a powerful army by sacrificing one or preferably 2 small cities. Obviously they should not be on prime commercial sites but only need work a few farms. If the war goes well, and it should with 10 drafted units plus the extra ones built with slavery as the cities are whipped down to size 2, you will have traded 2 second rate cities for a huge army and probably conquered one or two enemy empires. Meanwhile the big cities in your empire get the +2 happiness from Nationhood to resist war weariness.
That is what I recommend Sisiutil tries in this game to fully exploit the power of Toku's traits.