Yes, you can usually any brand of
eyepiece of the right size in any
scope - current standard sizes are 1.25" and 2" barrels, though some older/smaller
scopes may still use 0.965" barrels, which are harder to find good eyepieces for these days.
Best quality eyepieces are probably Televue - especially as far as ultrawide designs go - with prices to match - but there are several other high quality brands around. It's a bit like high end audio gear - you can pay premium prices to get the last bit of performance, or pay quite a bit less for something with most of the performance, or go for something cheaper which works but has limitations.
In eyepieces, the basic plossl eyepieces are a nice improvement over earlier designs, and are quite usable - but premium designs can have wider fields of view, better eye relief at short focal lengths, and maybe better quality views - though the quality differences may be subtle. The field of view difference can be huge - especially with ultrawide designs - and the eye relief difference can be big too.
Basic coloured filters are usually of little use, apart from a
moon filter to cut the brightness down a bit - most people tend not to bother with coloured filters.
Narrowband filters are expensive and have specialised uses - they can help spot some types of nebulae by making them stand out more - but all filters give you a dimmer view; what they can do is boost contrast by dimming unwanted colours more...
Light pollution filters are useful for imaging, but are no substitute for dark skies.
The eyepiece kits you see advertised can be worth considering - they're usually basic plossl eyepieces, and if you have the budget you'll probably end up replacing them with premium designs - but they're a relatively cheap learning resource - you can see how bright/big various objects come out in your scope with different focal lengths, so when you go shopping for premium eyepieces you'll have a better idea what to go for...