Creating symmetry in 2 new flower beds

I've attached a drawing of my garden which I am currently re-landscaping and would love some recommendations for plants please. The garden is approx 12ft x 17ft, west facing with acidic soil. I have got rid of the awful grass lawn and skinny borders and am replacing it with two larger borders and a slate path and seating area which is shaded in in the diagram.
I'm now trying to chose the plants and am struggling to visualise it all. The right hand wall and the bottom wall are both about 3ft so I want to limit the height of plants there to about 3.5ft max. However the left hand wall is next to the pathway to the house and reduces in height as it goes, from about 1.5ft down to about 9in.
I'd prefer to go with a traditional plan with evergreen shrubs at the rear and smaller plants in front etc. But the problem I'm having is trying to get some sort of balance between the shrubs on the left and shrubs on the right. I don't need them to be identical but I'm concerned that if I chose a large variety of shrubs it will all just look like a mish-mash without any harmony between the two beds. I think I would find it so much easier if both walls were the same height but I can't change this.
I'm inclined to go for an informal/cottage garden look. I'm not exactly a novice gardener but in all previous gardens I just inherited established beds and added bits and pieces here and there as I went along.
I would appreciate any advice about how to create a balance please, particularly with the evergreen shrubs. (Please ignore the extra dotted lines, that was a previous plan but I've run out of paper.
) Thank you.
I'm now trying to chose the plants and am struggling to visualise it all. The right hand wall and the bottom wall are both about 3ft so I want to limit the height of plants there to about 3.5ft max. However the left hand wall is next to the pathway to the house and reduces in height as it goes, from about 1.5ft down to about 9in.
I'd prefer to go with a traditional plan with evergreen shrubs at the rear and smaller plants in front etc. But the problem I'm having is trying to get some sort of balance between the shrubs on the left and shrubs on the right. I don't need them to be identical but I'm concerned that if I chose a large variety of shrubs it will all just look like a mish-mash without any harmony between the two beds. I think I would find it so much easier if both walls were the same height but I can't change this.
I'm inclined to go for an informal/cottage garden look. I'm not exactly a novice gardener but in all previous gardens I just inherited established beds and added bits and pieces here and there as I went along.
I would appreciate any advice about how to create a balance please, particularly with the evergreen shrubs. (Please ignore the extra dotted lines, that was a previous plan but I've run out of paper.

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https://forum.gardenersworld.com/discussion/comment/2209185#Comment_2209185
Just been trying to find it but no joy.
It had a small zig zag path and ended with a wall at the end where they had a seat.
@B3. Personally I'm quite happy with the path as it is as it suits my needs. Yes, it might look odd on paper but in reality it looks fine. What alternative would you suggest?