I’ve found a few resources which I’ve listed below. Otherwise, here are a few tips that might help you out with this.
Think About How Magic & Technology Would Interact
Personally, I think it makes more sense for the technology in the world to be powered by the pre-existing magic… but of course, that’s not an absolute rule and by all means, the magic doesn’t necessarily have to exist before the technology.
However, it is important to think about how these two elements interact. Imagine if it was commonplace in our world for people to wield energy. Do you think we would be using that to power electrical devices and the things we rely on, or would we still burn through our natural resources?
What would weapons look like, what kind of devastation would they bring? How would the way we educate our children change, and what kind of professions and skills would emerge out of this new magical era?
Think about the science and machinery we already have. What would happen if we added magic into the mix?
The more you know about the world you’re writing, the easier it is to work with. What is the ‘norm’, first of all? Once you know what can and cannot be done between these two things, then you know exactly how much room you have to play in. It also helps the reader get a grasp of the world’s laws, keeping things easy to understand and most importantly, easy to imagine.
Consider the Environment
I’m really showing my nerd colours today, but there were a couple of games that sprung to mind when you said this, where I think the combination of magic and technology is done well. The first being FFXIV: A Realm Reborn.
It’s a MMORPG; in the world of Eorzea, you can play as characters such as Black Mage, White Mage, etc… Typically, magic-wielders, who use Magic Points as power behind their attacks/spells. Having played through the WHM route, there was a heavy emphasis on the interaction between the use of magic and the direct effect it had on the environment.
Whilst some believed using the magics of the natural world was exploitation, others saw it as a way of establishing harmony between Eorzea and the elementals, proving the two could coexist and help one another.
Anyway, in this world of magic and mystery, there is also the Garlean Empire who have advanced technology known as magitek (something which appears in VI too). As you can imagine, it’s a mix of magic and technology. The machines the Garleans create are powered by ‘Ceruleum’, a powerful, unstable form of energy.
In the game, there are a couple of areas where Garlean territory lies in the midst of the almost medieval-style, magical parts of the realm. They have huge, metallic structures and bases, patrolled by soldiers and weaponised Vanguards. They’re heavily associated with - and tied to - very unnatural practices and materials. The magitek mount is animated machinery, powered by the magics already present in the world (as Ceruleum is mined or created by draining elemental crystals).
All I can say is that it looks pretty unnatural to move from the earthy, rocky settings of Western Thanalan (desert-country) into Cape Westwind, to name on example. So it’ll be interesting to think about how the technology appears in comparison to the magic, assuming the latter is natural, of course.
Consider Technological Advancement
Another game where this kind of mechanical-magical merge is prominent is Lost Odyssey. This is set during a magical industrial revolution, in which the sudden increase of power in magic brings with it a huge amount of weapon-tech, including machinery which can harvest the power of certain elemental magics to further research and industrial expansion.
In the game - although I haven’t played it for many, many years - I remember walking around the cities and seeing the magical generators and machines that saw to the upkeep and maintenance of everyday life.
Also, technology is something that some countries aggressively pursue whilst others don’t. Industrial revolution might not happen everywhere at the same time, so it might be useful to think about how different aspects of your world are affected, specifically how the balance between the two comes across from place-to-place.
Anyway, these are just very basic things to think about. It’s always useful to keep an eye out for follower responses too as you can get some suggestions that way. Otherwise, please find resources below!
I hope this helps… best of luck…!