These are different strategies in accumulating Bitcoin. Some investors use DCA strategy, others prefer buying the DIP strategy, while some DCA and also reserves funds to also buy during the DIP and some accumulate with lump-sum (Rich folks). All these approach are decisions made individually with what suits our bitcoin investment goals.
As an investor, we have to put in consideration all of the strategies you have mentioned here, also, combining them as well is never a bad idea for those who may desire or like to have a combination for one or two strategy, but before we can start any of these approach, we have to get a means of identifying the kind of investor we are, how long we are targeting for the investment as well as how much we are investing in for that particular reason, this will help us towards achieving for the required means for the best our of interest over what we are investing, also, we can be able to position our targets on the right time and plan ahead in other to avoid having uncertainties in the way we invest, hold or sell at any particular time.