Offer sheets are for the naive. They make zero sense for players at this price level. Also the silly detail about players having to actually sign them, knowing they may easily be matched, now creating friction with your team.
Going to arb is also nothing more than a negotiating tactic. Necas will agree to something before any actual arb hearing. Nothing to see here.
Marner and Draisaitl are two different situations.
Toronto would prefer to get rid of Marner. They don't want him back. The fans don't want him back.
The Oilers want Draisaitl to stay. The fans want him to stay. The player has indicated he loves it there. The team had a busy time in free agency, without an official GM, so they might prefer to hire a GM first. The player had less than a week between losing Game 7 and being able to sign an extension. He took a vacation. They will sort out an extension later this summer. There is no drama.