Junior has always use electronic on a TT bike (except Nationals age 9). You can save some money, some weight and get more aero just doing 1X
Depends on the course of coarse, but 1X works great for the ITT and esp. if it is a narrow/wide ring then the chain is likely not coming off. We got the LUX juniors repositioning their read cassette cogs for straighter chain alignment. Some of that stuff, I'm convinced (and so is he) placed junior ahead of stronger riders.