I used Home & Business (download version) in 2018. For 2019, I don't need Business. If I purchase Deluxe, will TT auto-detect basic info from my 2018 to prefill 2019?

Yes--- as long as you have the 2018 tax file on your hard drive it is simple to transfer it to your 2019 desktop software; the software version does not make any difference for that.  You will be asked when you open the new program to start a new return if you want to transfer a return.

https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-turbotax-online/00/25953