I've heard incredible things about SIP containers but have yet to try them myself. I was actually considering this method alongside the blumats. SIP containers are wonderful, but the only issue with them is how pricey buying all that perlite can be after a certain amount of pots. If you only have one or two pots you're doing this with then it shouldn't cost much, but if you're doing dozens upon dozens of plants this way the cost of perlite will add up quite quickly. SIP is good for a small scale grow, but should you decide to expand your grow you'll find the costs for SIP get quite pricey and Blumats would actually be a cheaper solution. SIP is great though because, like the blumats, it essentially puts the soil in charge of water uptake via wicking.
There are two reasons people will typically "cook" their soil and the phrase "cooking your soil" can actually refer to one of the following two reasons. The first reason to cook your soil is dependent on the organic amendments you chose to use. Things like kelp meal, neem meal, crab meal, and the like decompose quite slowly over time and as a result don't need to "cook" because it isn't decomposing at a rapid rate. Conversely, amendments like blood meal, alfalfa meal, and any kind of guano decompose rapidly. I'm not sure if you have a compost pile or have ever toyed around with one, but a compost pile can get upwards of 160F depending on how quickly the material in it is decomposing. So typically when people say "cooking" they actually mean decomposing.
Your kelp or crab meal will react slowly with the peat and things won't get too hot if you choose these types of amendments, so you typically don't have to actually "cook" the soil, only inoculate it but I'll get into that below in a bit. Since kelp/crab/etc meals don't decompose very quickly, the soil will never get too hot so you don't need to allow it to decompose before using it. Manure works kind of the same way, using straight manure puts you at a high risk of burning your girls, so it's better to combine the manure with peat moss and let it sit until it becomes compost.
However when you use something "hot" like blood meal and guanos they decompose at such a rapid rate that it'll straight bring the temps of your soil to anywhere between 100-160F. In this case, cooking (letting it decompose first) is mandatory otherwise you run the risk of exposing your roots to the above temps which will kill them off right quick.
The other reason you'll see people use the phrase "cook your soil" is in reference to inoculating it with the microbes that will actually process all of your organic material. The C:N reactions will decompose these materials over time, but not nearly as quickly as microbes will.. plus your microbes are what build a relationship with your roots, not the amendments we use, so we definitely want microbes going as soon as possible. Fortunately, inoculating your soil is incredibly simple now ever since I stumbled across the "Growers Recharge" product that I can't recommend highly enough. You used to have to brew an EWC and/or compost tea of some sort to inoculate your soil with, now you can just grab a jar of recharge, mix 1/2 tsp of it per 1 gallon of water and you're good to go. You could even use a fish hydrolysate/emulsion to inoculate your soil. Fish hydrolysate and emulsion are also products that I just can't recommend highly enough, but as you pointed out they stink! Keep the scent of fish/seafood products in mind if you have cats, I have to be careful watering my veggies with the stuff because it drives my cats insane xD
As for direct sowing the seeds, that is definitely the absolute best method to use to start seedlings.. however it does come at the cost of a learning curve for sure. Using the paper towel method is pretty much foolproof in terms of getting high germination rates.. the problem with the towel method though is that sometimes the roots grow into the towel and have to be ripped out which can cause issues. Furthermore, the seedlings can be planted improperly also causing issues.. and issues at that stage can be life and death.
The reason direct sowing is difficult is because instead of using a towel/bag to control the moisture and humidity, you now have to do so yourself. Your soil has to be perfectly and consistently moist to direct sow. If the soil is too wet the seedling will die the instant the taproot pokes out as it will drown. If the soil is too dry, it straight won't do a damn thing. If the soil gets too dry when the taproot comes out, it can wither and die quite easily. If you're wanting to direct sow, a pump sprayer will be your best friend because it will help keep your soil moist without adding too much water, and at a gentle mist that won't disturb your seeds. Direct sowing is the shit, especially if you direct sow into the final pot. The plants will never see transplant stress and will never experience shock in the seedling stage, which translates into faster growth
Just keep in mind that it is at the cost of a learning curve and is something that will need to be dialed in. I can get 90%+ germination rates all day with the towel method. When I first attempted direct sowing though, my germination rates went down to 40-50%. Using my pump sprayer to water direct sowed seeds has brought my germination rates back up to the 90% they once were at, but it took a bit of troubleshooting on my part.
HTH!