Your best views of planetary detail require both aperture and focal length. You need enough aperture to provide a bright view at magnifications above 150X, which generally means a focal length of at least 900mm.
A 4.5" reflector can do this, but just. You still want a good focal length.
I have seen very good views of Saturn and Jupiter in the Orion XT6 reflector. It provides enough light for a decent view at 200X, so it's good for planets. A 6" refractor would be better (since there is more contrast and light due to the clear aperture), but its disadvantage would be that it's very big, requiring a solid mount, and more expensive.
A 6" reflector is on the low end of "usable" for galaxies and other DSOs. So, at minimum, I'd recommend a 6" reflector.
An 8" would be better and a 10" better still.
If more than 75% of your observing would be the Moon and planets, then a good 4" refractor (something like the Celestron 102, minimum) would be a good choice. It will still put in some galaxies and nebulae and would do a good job on the planets.
On a typical night, the instability of our atmosphere will limit you to magnifications of from between 250X and 300X, which is were really detailed planetary views normally begin. But even on an average nights there will be moments of steady seeing that will make it worth your while.
So, on balance, I'd suggest either a 6" (150mm) reflector or a 4" (102mm) refractor with a minimum of 900mm to 1,000mm of focal length.
For eyepieces:
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Moon: Just about any focal length is fun, but a 15mm and a 10mm would be great. Nothing shorter than a 4mm at the above focal lengths, however.
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Planets: Either or both of a 5mm and an 8mm for good detail at the apertures above.
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Galaxies: 25mm or 10mm would be good at the above apertures and focal lengths.
Notice that if you have a 25mm and a 15mm eyepiece plus a 2X barlow you can pretty much cover the above range, except at the extremes.