Cheaper and easier is 1x10. Won’t need new shifters or wheels, would just need a 9 Mtb speed derailleur. I run 8/9 speed Deore with 10 speed 105 upfront.
Other derailleur work, but if they don’t have a barrel adjuster you need to add one to the housing near the stem. You could add a derailleur extender to get up to 40t if derailleur capacity is lower.
There are 9 speed long cage, Shimano Altus for example can go up to 40t.
Or get a 10 speed road and add a roadlink, should be able to do 40t in back with that.
Narrow wide is advisable but not essential. I don’t use one on my cx 1x10 setup and have no issues with dropped chains riding single track. Just make sure the chain is the right length. Narrow wide with a clutch derailleur is overkill but nice, my mtb is setup that way. Clutch on its own is supposed to remove the need for narrow wide.
__________________
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Last edited by pyze-guy; 06-09-20 at 08:07 PM.