For your Lexus. M1 is a good oil, particularly if you want something that is easy to find. Instead of 5W-30, you might try their 0W-30. Fargo winters qualify as 0W country
. 6K mile OCIs on M1 should be a no brainer unless you are doing a lot of Fargo winter short trip driving, then you should try an OCI once at about 4k miles or so to see how it's doing.
As long as the DeLorean is only getting driven when it's over 45F out (over 20F would be warm enough) a good HDEO 15W-40 like Delo 400 or Delvac Super 1300 would be a very good oil for it. For both the engine and the flux capacitors.
The concerns about 10W-40 are mostly based on older oils, although I would still be leary of cheap modern 10W-40 oils.
Its probably a good idea to change your oil at least once a year, so as long as you are driving your DeLorean at least 6k miles per year, a synthetic xW-40 would also be a good oil. If you drive it much less, then a good non-synthetic HDEO makes more sense.
You can't go wrong with a NAPA Gold filter. Wallyworld ST filters are real bargains and reports are that they are good filters. Purolator filters are good too, particularly the Pure One line. I don't think you can really go far wrong with any good brand name filter except those made by Fram.
My favorites from walk in stores are Napa Gold and Purolator Pure One. If I were on a tight budget, it would be Wallyworld ST filters or some other house brand Champian built filter.