I don't know. In general the attempts will be made to show that certain categories of ballots are not valid and then let that determine the outcome of the elections.
And unfortunately most of the challenges will be in state courts so you cannot predict one uniform response to certain irregularities. A reasonable mind not familiar with the law might conclude that challengers must demonstrate probable material fraud to disqualify certain ballots but I cannot say that will be the case in all states. In many/most cases a simple showing/proof that the statutory requirements for a valid ballot have not been met regardless of whether fraud was or was not intended. You know you have states that have mail in ballots that require you to have your vote witnessed, and include the witnesses signature, that the ballot be placed inside an envelope-sleeve and then that be placed inside the mail-in envelope and it must be dated and received by such and such date. Every state has some combo that met or other requirements. Whether all of these must be met or the spirit of the law must just be substantially met is where the fun begins and the lawyers get rich and the days drag into weeks for finalizing the count.
Fun, fun, fun ....since daddy took the T-Bird away.