Both would be at the top of the list of the most likely theories.
If you take out stranger abduction then you have either the guy with her on video and with witnesses, showing and talking about her condition... Or the boyfriend that she'd not met up with that evening, not (apparently) contacted, and she was out with someone else leaving him with the most obvious (and classic) motive.
So it would make sense they both have the most to fear from LE and prosecution and could be the most fearful of being wrongly suspected. Which could explain their 'distance'.
CR has MB and JR apparently alibiing his story though (and maybe JR had guests that also alibied him). No idea if JW has an alibi beyond 'sleeping' and how ironclad that could be (could he have left and returned undetected?).
So it's a conspiracy vs jilted boyfriend at the top of the list IMHO. ...Unless you believe that CR and MB are truthful and JR is the real culprit. But if he had houseguests then either they had to be in a position of no knowledge or also part of a conspiracy.
I've said for a long time that JW IMHO gets too much benefit of the doubt here. I think a large part of that is because the parents initially shifted the blame from him and I don't think they had good reason for that except that they 'knew' him and so it made it harder for them to see him as capable of anything versus these 3 men from 5N that they'd probably never heard of before. I think this was a mistake on their part. It narrowed public and media focus too much when there was a bigger picture to be explored.
I still believe the confrontation at Smallwood is odd and mighty coincidental not to have been some kind of a factor and/or a missing link in the case.
Again, I think the narrow focus has allowed this event to escape the scrutiny it otherwise would have. You'd think the media could investigate this more thoroughly and at least take some mystery out of it, or tie it to some broader possibilities. But when the public and media focus on the guys at 5N so thoroughly it makes the SW confrontation just seem to be a footnote in the timeline more than a crucial piece of the puzzle needing to be better explored.
IMHO....
I do understand why you are skeptical about the Smallwood encounter, but do you have any links pointing to where this was, in fact, actually NOT out of pure concern for LS? Every time CR has spoken to the media, he has been lashing out. Jupiter just posted how he is rumored to be acting on campus/in class,etc. These are all behaviors he demonstrates while completely sober. Based on that information, I don't think it's unreasonable to think his behavior while intoxicated could be extremely obnoxious and given LS' reported condition, I don't think it is unreasonable that strangers would be concerned. If CR responded anything like he has in the media, I can totally see a hot-headed kid punching him, especially if he had been partying elsewhere too.
I also thought ZO & co. were NOT friends with JW? I know it was initially unclear, but I thought it was later decided they actually weren't friends?
I definitely agree that JW should be critically looked at, but always in context. Sure, he had the classic motive, but there has been zero evidence even hinting that JW knew what was happening or was around (that the public has been alerted to). He was also the one to call the parents. I definitely think he should be looked at because he would have had the classic motive, fortunately or unfortunately. However, in my own opinion, he would only be the number 1 POI if CR, MB, JR, AND JR's guests had already been ruled out (and there are definitely scenarios that would not involve ALL CR, MB, JR, and JR's guests). I do think that JW should be examined before a random abduction though. Although both seem unlikely based on the known public evidence (JW wasn't around/might not have known about the night's events and the white truck was ruled out), at least JW would have motive.
I feel for the Spierers. I can at least come up with plausible reasons JW would no longer want to be involved (it sounds like LS and JW may have been on the rocks, he might have been furious she ditched him and sent some nasty texts that in hindsight look really bad), but none make it okay morally to not continue talking. Again, legally, I agree JW does not need to continue talks. Morally though, LS was his long-term girlfriend. I do not understand why he isn't doing more.
I have even less sympathy for the 5N boys. Unlike JW, they were with her that night. They saw (and probably provided) whatever she had. They were supposedly the last to see her. I understand the need to protect one's own interests, but I would hope that they would consider finding their friend as something in their best interest, even if it were purely for their own selfish peace of mind and removal from public scrutiny.