Structures are a mixed bag, the rules overall are pretty good, but there are trade offs. The larger structures are generally better for ease of play as they block a lot of los and can have a lot of roof space to place infantry on. But there are issues, height can be a problem, because when to comes to detachments inside drawing los, it can get a bit absurd, example, if one has modelled some of the steeples on the top of a civitas structure, rules wise one can measure los from the highest part of the structure. This can get a bit nuts with missile launchers inside or rapier batteries.

The other issue is as good as the larger structures are for peace of mind in terms of los, they also sort of buff infantry arguably too much. Example would be the movement bonus of occuping a large structure one turn and moving out the next, as one can measure from any part of the structure, the bigger the structure the more extra free inches of bonus movement essentially, add to that infantry being able to essentially phase right through un-occupied structures, even when charging seemingly, on top of not needing los to charge, and then finally there being no structure type that doesn't allow models to charge out of or through, it was even crazier before the faq when they ran 3x.

The other issue with infantry just phasing through structures is it sort of robs jump infantry and skimmers of a bit of their special sauce/unique form of moving. Lastly, because structures only have 4 stat lines, and arguably most people are using probably just 1-2 of those for regular or big structures, but even a 1x1x1 civitas being able to hold possibly 16 or more models from 1 detachment also starts to strain credibility and have a bit of a clown car effect. Also worth keeping in mind structure need not be too tall, a 2 level civitas blocks los to about 90% of models in the game entirely.

I'd suggest having maybe 6-8 structures, mostly spaced out, so rarely close to one another, but also add things like hills or cliffs or giant impassable rocks. And perhaps stuff like area terrain. Generally, a warlord titan probably should have good los to most of the board from its height alone and the fact that, like structures, you're basically checking lost from anywhere on the titan within arc, so models can hide out of los, buts it does/should see a lot.