Subs is usually the one that has more open spots than people who want them. Last year (class of '18) was an exception and there was no sub draft.
For '18, there was actually a SWO draft, but the people sent SWO (who didn't pick it first) mostly came from those who picked SWO NUKE as first choice.
Class of '17 was more typical.
86% got first choice
9% got second choice
2% got third
>1 forth
>1 fifth
>1 sixth
Also for '17, USMC came up 40 people short, but USMC does not draft those who do not pick Marines 1st choice.
Also, for '17, there were 74 mids who went to SARB (service assignment review board). If you get sent to the board, you are not likely getting your first choice.
Of those 74, 40 got Subs, 19 got SWO Nuke
Of the 40 that got Subs, they came from 8 SWO, 14 Pilot, 15 USMC, 2 NFO, 1 CW
Of the 19 that got SWO Nuke, they came from 8 SWO, 7 Pilot, 4 USMC
For OP - the metrics used to rank aviation candidates are:
OOM - 50%
Aviation Points - 35%
ATSB score - 15%
It is very possible that you could be ranked very high on the list, based on these metrics, but then be found "qualified" for Subs or SWO Nuke and be sent to SARB.
*Aviation points are awarded for aviation related activities and qualifications, ie. private pilot license, certified instructor, powered flight summer training, etc. etc.