Kappl is only 15km from the nearest exit on the Austrian autobahn. Therefore, if you take the google fastest route and keep to the speed limits the time will be pretty accurate.
If your route includes motorways in Switzerland and Austria then make sure you buy a Vignette (toll sticker). The Austrian one is cheap at around 5 euros for 10 days. Switzerlan has no option other than an annual one.
If you travel via Germany past Lake Constance then traffic can be very heavy, especially near Lindau.
Do not, under any circumstance let Google or your satnav take you near the B31 in Germany that runs from Freiburg to Lindau. It looks like an obvious alternative to the motorway but is horrendously overcrowded with traffic.
Personally, when travelling to Austria I go via Lille, Belgium, Luxembourg towards Saarbrucken (a good place to stop if setting off from Calais in the morning). Then head down towards Kempten to avoid Lake Constance. Cross over into Austria to get to Stanzach. No tolls on this route (unless you need a motorway sticker in Austria) and much cheaper fuel, food & accommodation through Lux & Germany.
Of course, you may have somewhere in France you need to be...
