Well... I think these are very similar (as you may be able to guess from the descriptions). I don't want to give any spoilers, but even some major plot points are similar.
The political scheming - which I would say is the focus of both shows - is a bit different in the sense that in 'Rise of the Phoenixes' the ML is an Imperial Prince competing for the throne (therefore there is a lot of infighting in the Imperial Family), whereas in 'Royal Betrothal' there doesn't really seem to be an Imperial Family outside of the ML and he is completely focused on retaking power as the Emperor within the Court/fighting external/hidden threats (external in the sense that they're outside of the State Apparatus, not meaning foreign exclusively) - which happens in 'Rise of the Phoenixes' as well.
The dynamic between the Leads is similar as well - Both ML's are born into high positions, but live a double life where they go undercover to investigate different injustices, which is something they cooperate with the FL with.
The FL is a 'Scholar' from a complicated background (though I would say Meng Tinghui's story is much worse, I mean they really put my girl through the ringer), who is also passionate about getting into government to serve, because they have a sense of justice - however the FL in "Rise of the Phoenixes' is hiding her identity as a woman. Because of this, the main couple in both shows also as interesting discussions about duty, politics and related things.
I'd say both ML's are also very scheming (and good at it).
The theme of a lost Kingdom and a secret society trying to pointlessly restore it is also present in both shows.
The political scheming - which I would say is the focus of both shows - is a bit different in the sense that in 'Rise of the Phoenixes' the ML is an Imperial Prince competing for the throne (therefore there is a lot of infighting in the Imperial Family), whereas in 'Royal Betrothal' there doesn't really seem to be an Imperial Family outside of the ML and he is completely focused on retaking power as the Emperor within the Court/fighting external/hidden threats (external in the sense that they're outside of the State Apparatus, not meaning foreign exclusively) - which happens in 'Rise of the Phoenixes' as well.
The dynamic between the Leads is similar as well - Both ML's are born into high positions, but live a double life where they go undercover to investigate different injustices, which is something they cooperate with the FL with.
The FL is a 'Scholar' from a complicated background (though I would say Meng Tinghui's story is much worse, I mean they really put my girl through the ringer), who is also passionate about getting into government to serve, because they have a sense of justice - however the FL in "Rise of the Phoenixes' is hiding her identity as a woman. Because of this, the main couple in both shows also as interesting discussions about duty, politics and related things.
I'd say both ML's are also very scheming (and good at it).
The theme of a lost Kingdom and a secret society trying to pointlessly restore it is also present in both shows.
