Firstly, avoid any firms that promise to take only 5% (or any other ridiculously low figure) of your earnings as tax. They’re fraudsters who somehow get away with peddling their BS and leave you to pick up HMRC’s tab.
Re JSA, I spoke with them last Oct when I was in a similar situation. Didn’t get on with the sales guy.
Spoke with Frankie at OrangeGenie. She was brilliant. Spent about an hour on the phone with me, answering every single question. No sales pitch. No BS. Turned out it was better for me to form a Ltd Company, so I chose OG to do that and handle the accountancy for me. Easy peasy and piece of mind. Online app (FreeAgent) is decent enough. They’ve built their own app as well (with rewards etc) but I’ve not played with it yet.
FTR, all my work so far has been outside of IR35.