I use betdsi and I think they don't give enough play-in options. But they will havd over/unders if you wanna do "middling". They let you play-in totals, spreads, and monelines/gamewinners.
Honestly, in-game wagering at a lot of books is a way to just lure more bets on both sides. Youwager for example, they purposely put out live lines on nights where they get heavy action and that side is losing just to get even more losing bets when people chase.
It's funny when there's nights where they say it's "a management decision" to not offer live betting
Best live betting for just totals and sides is probably betonline or sportsbetting.ag
Heritage just added live betting but I can speak for their software. Bovada has live betting, too, but it's mostly weird prop shyt that's pretty useless unless you're a complete degen who wants to wager on how far the kick returner brings the ball back or some shyt