MacPlus Software currently lists the ActiveDock 2 Pro deal first: ActiveDock 2 Pro With Lifetime Updates And Support for $47.99, best for you if you want a one time purchase of the Pro dock with lifetime updates and support on a single Mac. That $47.99 price is a fixed one time purchase and applies to selected items while stock lasts, and it cannot be combined with any other offers.
If you only need ActiveDock and want lifetime updates: buy the ActiveDock 2 Pro for $47.99. This is the exact price shown on the page and the clearest one step purchase for that product rather than trying to use a percent off on a different ActiveDock listing. The 20% off Activedock 2 single license is a website only sale on the single license version; the break even original single license price where the 20% sale would beat the $47.99 Pro price is $59.99 (because 0.80 × $59.99 = $47.99). If the single license list price is below $59.99 after stock and availability checks, the 20% sale could cost less than $47.99; if it is above $59.99, the $47.99 Pro deal is the better buy.
If you want DockView: buy the DockView Lifetime License for $39.99 when you want a one time lifetime license. There is also a 21% off Dockview 2 standard sale; the sale gives a lower price than the $39.99 lifetime only if the standard full price is under $50.62, because 0.79 × $50.62 ≈ $39.99. If the standard full price is higher than $50.62, the $39.99 lifetime license is cheaper.
If you want Command-Tab Plus 2: the listed lifetime price is $39.99, which is a straightforward one time purchase. The 22% off Command-Tab Plus 2 standard sale will be cheaper than $39.99 only if the standard full price is under $51.27, because 0.78 × $51.27 ≈ $39.99. If the retail standard price on the site is above $51.27, the $39.99 lifetime option saves more.
If you want the cheapest single tool and do not need Pro or Lifetime for that product: the MultiDock lifetime license at $28.00 is the lowest priced item on the page and is the pick if its features match what you need. All listed deals say selected items only and are available while stock lasts, and each states it cannot be used with any other offers.
When choosing between applicable options, compare the final totals and take whichever leaves the lower total, using the break even original price points above to decide whether a percent off sale on the standard product is cheaper than the fixed lifetime price. Do not assume offers combine; the listed terms explicitly say selected items only and that offers cannot be used in conjunction with any other offers.