Here some places that can be ok along the route you have in your map in order of your tour:
1) Althm?hlsee / Grosser Brombachsee (approx 50km South of N?rnberg)There is a rental place that has both Windsurf gear and Wingfoil at Altm?hlsee (
www.surfcenter-altmuehlsee.de/) . Wind is a bit hit and miss at this time of the year. If there is a cold front coming in you can get 15-20 knots and equally if it's an Easterly wind period you can get similar strength otherwise it's mostly light wind. This used to be my homespot.
Grosser Brombachsee gets a bit better wind but don't know if there is a rental place there these days.
2) Ammersee (approx 40km South of Munich)The best out of the 5 lakes. Wind is a bit better than the previous lakes. Best spot there is Herrsching. Awesome when it's either a westerly or "F?hnsturm" (unusual at this time of the year).There is a rental place there from memory but can't find the link at the moment.
3) Kochelsee / WalchenseeWhen it's sunny and warm the west side of Walchensee get's a thermal wind in the afternoon (approximately 15 knots). There is a campground with direct lake access in the town of Walchensee but it's busy during school holidays (I think spring holidays are coming up at the beginning of June.
Kochelsee can get super windy early mornings (6am - 9am). It needs a Southerly wind flow to work and get turbo charged when there is a F?hn wind blowing (low pressure South of the Alps / high pressure system north of the Alps) but again that doesn't happen too often in early summer.
4) Gardasee (Lake Garda) (approximately 350km South of Munich)Gets crazy busy during weekends and in school holidays when half of Munich invades the place. The sailing happens mainly in the North of the lake. Both Torbole and Riva have campgrounds. Torbole has the better wind / campground water access combo in my opinion. There are a few campgrounds along the East side of the Lake but don't go South of Malcesine as the wind get's too light.
Main wind directions are:
Northerly (Vento): Blows in the morning. Best when there was a thunderstorm in the hills behind Torbole over night or if there is a low pressure system in Southern Germany and high in the gulf Genoa. Best between Malcesine and Navene (East side) and at Capo Real (West side).
Southerly (Ora): Blows in the afternoons. There is no Vento in the morning and it's sunny. Best wind is between Hotel Pier and Riva along the cliffs. But can be good from Malcesine towards Torbole.
Westerly (Ponale): If there is a thunderstorm in the hills west of Lake Garda you usually get a squally storm pushing out onto the lake. Wind can often reach 50knts.
There are a few rental stations around the lake. There its a Dutotone Pro Center in Torbole at the yacht club and there used to be a rental at Hotel Lido Blu.
On the westside there is Hotel Pier (great for Ora / ok for Vento) and Hotel Capo De Ramol (great for Vento / ok for Ora).
5) Italian Northern CoastThere are some good spots but rental places are far and in-between and I wouldn't go there specially for windsurf / foil holiday.
6) Lake ComoGets thermal winds but not as good as Lake Garda.
7) BodenseeGets some good winds but only ever sailed there a couple of times.
RE motor homeIt's worth mentioning that most lakes around Europe either completely restrict motor home parking (eg Lake Garda) or charge a flat rate per day / night (eg Altm?hlsee). Expect to find a lot of height barriers to prevent people from camping in parking lots at the lake. The barriers are often removed in Winter but in summer the expected to get a ticket if you park illegally.
RE taking gear. Only worth it if you go for a dedicated windsurf trip in my opinion. Good idea only taking a big wing / foil and buying a board locally. Don't expect the same level of used market we have here in Australia. Even though more people windsurf / foil the used market has always been seasonal and availability / range a bit hit and miss. Maybe try Marketplace before you arrive. Surftools is ok. There is also Surfstadle at Ammersee. Nuremberg has a couple of board shops and there are a ton at Lake Garda.
In Munich check out the Eisbach. There is a river surf spot with a standing wave in the middle of town. Google it ... not hard to find.