I know this thread is multiple months old. I wanted to give an answer to your questions incase someone else might have a similar question.
The difference between the BAP solution and powder is that you will need to mix your own solution if you buy the powder. Usually the hormone solutions come in a dilution ratio ( Something like 1mg / ml ). The solution helps you accurately dose the media you are preparing or the wash you are preparing. Normally, when you have the powder form of the hormones you will also need to invest into a good mg scale with a protective shell in order to make accurate solutions. In the past, I have always used the prepared solutions and stored them in the fridge.
Some tips that I learned over the years when I was doing TC. Baby food jars can be expensive. The PP (polypropylene) lids for them can also be expensive. I switched over to PP (polypropylene) deli containers with PP lids. I used the deli containers for growing out the cultures before they were transplanted into pots and hardened off. You can buy these deli containers from webstaurant store for rather cheap and they will last multiple cycles through the autoclave / pressure cooker. If you go the deli container route, make sure the containers and lids you are buying are polypropylene and not HDPE or you will have a melted mess of plastic after the autoclave process. Some links below.
https://www.webstaurantstore.com/choice ... 8BULK.html
https://www.webstaurantstore.com/choice ... 2BULK.html
https://www.webstaurantstore.com/choice ... LBULK.html
For starting cultures I used 50ml Polypropylene flat bottom centrifuge tubes. These are also not too expensive. I believe they come in bags of 50 for around $20 bucks. Even though the tops are HDPE, they are designed to be autoclaved.
I also highly suggest to invest in a box of Parafilm. This will seal your cultures and prevent bad stuff from getting in.
https://www.amazon.com/dp/B004VQP6CQ/re ... 7fc737124
Also, invest in a gram scale. This will make your process more accurate and the notes you take easier to replicate and trouble shoot. Especially when it comes to agar mixing.