I think a passive buy and hold strategy is the best option. Maybe half of the Top 20 could potentially see the bottom drop out and a few may trade up and down but a few will skyrocket so high that it wont matter...it would only take 3-4 of them working out to make this your best option at this point.
Top 20 Coinmarketcap i think already safe to trade or hold. At least their developer stilll develop it or maybe it still have strong community so they are on top coinmarketcap. Make it as long investment is good to do.