Since the OP has said she wants a rear facing seat is it really useful to come along and have a discussion about how you personally don't want to rear face?
OP has hardly said everyone should rear face. She's just looking for a recommendation for a car seat.
Squidge - it's pretty rare to get to around 20kg and suddenly find they are car sick. It tends to be either from birth or around age 2 if it happens, and you get some indication earlier because they tend to be generally uncomfortable/unhappy in the car just without actually puking. There is also some evidence that direction doesn't affect travel sickness. I'm not sure about this, because I get travel sick myself and it does seem to be a problem for me, and anecdotally I've heard of plenty of DC who are less sick travelling forwards, but the research does seem to suggest it makes no difference which might mean there are things you can do to mitigate it regardless of direction.
But if you are likely to have another child, this is absolutely a decision you can postpone, because eventually you'll need two seats in the toddler stage. So even if you get a really long lasting RF one for DD and then a year into using it she suddenly starts puking everywhere, you could get her a FF seat and keep the RF toddler seat for DC2 (who will hopefully not be travel sick!) If you only plan to have the one child, it might be something you want to think about earlier. But I'm not sure how common travel sickness even is any more, I know for me it was massively exacerbated by my parents smoking in the car, which is very rare now, so it might be that it's actually become less common. I don't know if there are stats anywhere.
I would not recommend any seat which goes rear facing up to 18kg and forward facing after that, because they are all combo seats with a booster and these tend to perform poorly. They also tend to be seatbelt fit which means that the child is in a very reclined position like an infant carrier with very limited leg room, and the seatbelt is in the way when putting them in and out. They are OK for spare seats or if you're on a tight budget, but if you can afford to spend more, I would recommend you get a seat which is dedicated either to the 0-18kg stage or 9-25kg stage, and then get a separate high backed booster later on which can do the HBB job well. High backed booster seats are about a quarter of the price of toddler seats, so it's not something you need to be saving on by bundling it into another seat.
There are a lot which go both rear and forward facing so if you're unsure about committing to RF for the whole time this is what I'd look at. There are loads of these up to 18kg - I could probably list them all but I'm coming up with more than 15 just off the top of my head! If you think there's a significant chance you'll use it FF, I'd look at one with a high safety score from ADAC - I can look these up in a bit if you want. I need to go and do bedtime now (am an hour ahead of UK).
Up to 25kg there is just the one that can go both ways which is the Diono Radian 5. It's not my favourite 25kg seat, it seems to be a bit marmite among the car seat world, but it is solid and it does work.
Having said that, I do think that once you get past about the age of 2, if you have a rear facing child they are likely to be more comfortable in a 25kg seat, so these are a better investment if you're totally certain about rear facing.
I have to admit to you I have not personally had a child rear face yet any longer than 21 months (which is the age of my youngest! DS1 was 18 months when he went forward, it was 10 years ago) but if you go on the rear facing car seat groups on FB you will see plenty of rear facing 5 and 6 year olds and the members report that they are very comfy and/or that they complain once they switch to a forward facing booster seat. You could do a search for long journeys or add your own question about long journeys. I will say long journeys was one reason we decided on a spin seat, because we thought if DS2 gets really grouchy during a long drive (we do 10 hours + breaks, so it's a long day) and he's old enough we're comfortable with occasional FF then we can try a different direction for him.
If I had to recommend one seat up to 18kg RF - either Axkid Modukid, or any of the well-rated seats with the spin function.
If I had to recommend one seat up to 25kg - Britax Max Way Plus, or Besafe izi Plus X1. But yes, the Axkid seats are brilliant as well. They are all good really!