@jmaunsell thanks so much for reaching out about trekking poles! We've had some really good conversations here in the community on this exact topic - you can find a few one of those conversations here.
Also, here's a great resource in our Expert Advice on How to Choose Trekking Poles.
And finally, a few thoughts:
- Telescopic are likely a better choice for what you're describing, as you can shorten them for the uphills and lengthen them for the downhills.
- Shock absorption can be really helpful if you're covering a lot of miles and/or using them repetitively
- And then there are some personal choices, like material used in the grip (cork, rubber, foam)
Hope this helps to get you started!