Generally if you want to get out into rural areas and the Highlands then it's much better to have a car.
Public transport in the cities and more populated regions is generally pretty good, but when you get out into more rural areas, particularly in the Highlands, it can be sparse to non-existant. Although tours can often be a good option, they do have obviously have the limitations you mention.
However, from your posts it appears you are staying in Edinburgh and Glasgow? I would recommend against having a car in these cities because it is generally not that easy to drive/park in these cities due to congestion, trams, oneways and bus lanes with enforcement cameras and limited/expensive parking in many areas. Also, if you're trying to drive in and out of these places for day trips you may find you waste quite a bit of time in traffic jams.
Lastly Scotland is larger than many people think and as such there are large parts of the country that simply aren't reachable as a day trip from Edinburgh or Glasgow. Edinburgh in particular is far from any Highland scenery. As such I'd really try to plan out basing somewhere other than Glasgow and Edinburgh, most likely to a good bit further north (or perhaps one of the islands if they're of interest) for at least a few days of your trip. So you maybe spend a few days in Edinburgh and Glasgow (or do one at each end of your trip) without a car then pick up a car to head to a Highlands/islands base.
If you're tied to the cities because if business or a conference or something then I'd think twice about getting a car and stick to tours or public transport, despite their flaws. There are plenty interesting places more close by that are easily accessible by public transport from the cities - for instance Arran or Loch Lomond from Glasgow or St Andrews from Edinburgh.
I'm not an expert on photography but I think an awful lot of places all over Scotland probably offer good photo opportunities one way or another. In terms of castles these are all over too. Obviously the most famous ones are at Edinburgh and Stirling and these are easily visited without a car. Other well known castles in rural locations like Glamis, Blair Atholl, Doune etc are within day trip distance of Glasgow and/or Edinburgh and some are covered by tours too.
In terms of Scotland's true cuisine then it's probably not what the tourist marketing would tell you it is - most people don't like/never eat haggis - Indian food and curries are infinitely more popular! Generally a lot of Scottish foods that are widely consumed are fatty or sweet, like fish and chips, Aberdeen butteries, Scotch pies and Irn Bru. However, if you're interested in fine dining then there are a growing number of upmarket and Michelin starred restaurants using Scottish produce to make top quality cuisine.
Alcohol is very popular and in addition to the whisky distilleries there seem to be an ever growing amount of small gin distillers and craft beer breweries.
I think wrt Scotland's true culture we could say similar. It is all too often promoted abroad as people in the Highlands wearing kilts whilst they play the bagpipes and do the Highland fling, but again, whilst this is a part of Scottish culture, the reality is that most people in Scotland live in urban areas or cities and rarely/never do any of these things. As such scotland's true culture is arguably more modern and includes things like sport (particularly football!), fashion and contemporary music, art and architecture etc. Nevertheless the tartan and bagpipes seem to sell well and as such some places that are very popular with tourists are almost arguably somewhat "dressed up" like this, so of you want to see a more genuine example of modern Scottish culture and cuisine you may need sometimes to look beyond these places.
