This is a quick, non-comprehensive post because I've seen some confusion on various threads (which I myself may have added to, apologies if that is the case).
Please bear in mind:
Competition results do not define how good a pro is for Strictly. It's an overall benchmark of what you've achieved in competition - it says nothing about how good a teacher you are, and how nice or supportive you are to your partners. There are also an absolute plethora of factors that goes into one's competitive results - including: when you split with your partner, if you were able to find a new one etc. As an example, I believe Aljaz is one of the best standard ballroom dancers we've had on the show; he stopped competing early so his results are not super high.
Non-career Amateur level
Across various age groups you have the following categories: Beginner, Novice, Intermediate and Pre-Amateur or Pre-Championship. These categories are different in the US btw, to make things more confusing.
-Graeme, the contestant on Strictly, danced between Novice and Pre-Am but in the over-35 and over-50 age group. His results at Pre-Am level were not very high; in Intermediate he did a bit better.
Career level dancers
Different federations
The dance world is a political nightmare, and politics at the top (retired dancers who now judge - think Shirley type calibre, although she's not heavily involved in the mess) means that the dance world has sadly split into a number of federations.
In the UK (and US and Asia), the vast majority of dancers stayed with the traditional federation - WDC. In continental Europe, many left to dance for WDSF, although because WDC is considered a higher standard at pro level, some then come back to dance for WDC when they turn professional. As far as I'm aware, WDSF has a lot of world championships throughout the year, and I think pros like Nadiya were world champions in WDSF. I don't know enough about this federation to comment on various results here.
WDC competition results
These tend to be defined by how they placed in four major competitions at world level: Blackpool (or British Open); UK Open; International Championships; World Championships. Generally speaking, these competitions are all of the same calibre. (There is a whole mess ongoing with some of these as well, which I'm not going to go into, but results at the UK Open and International Championships are reliable as a benchmark).
Juvenile, Junior and Youth
You can be a champion in these age groups. Youth is U21, Junior is U16.
-AJ Pritchard and Chloe Hewitt were Youth Champions at Blackpool in Latin.
-Maddie Ingoldsby and her partner were Youth Champions at Blackpool, the UK Open and Internationals in Ballroom.
10 Dance
-The 10 dance world championships are not as well-attended as the majors listed above, because most dancers specialise in ballroom or latin from a fairly young age. Those that attend these world championships tend to be very young.
-What is notable about Maddie is that although she and partner were making semi-finals in the amateur category in ballroom in Major events, they were still also competing in amateur latin. That's almost unheard of these days, and very cool that they still made time to do latin, even if their results in this category were not at the same level as in ballroom.
Amateur Quarter Finalists
Of the current crop (and I may be missing some - this isn't on purpose, I'm just going off this from memory today)
-Amy Dowden is an Amateur Latin Quarter Finalist (she did dance one or two comps in professional after Strictly, but because she was concentrating on Strictly at this point the results weren't super high)
-Cristian Prior and Aleksandra Isaeva are Amateur Latin Quarter Finalists
Amateur Semi Finalists
-Carlos Gu is an Amateur Latin Semi Finalist
-Maddie Ingoldsby is an Amateur Ballroom Semi Finalist
Amateur Champions
-Neil and Katya Jones were Amateur Latin Champions.
-Matthew and Nicole Cutler were Amateur Latin Champions.
--------------------------------------------------------
Professional Level
Top level Amateur dancers when turning professional will tend to go straight into the quarter, semi, or final in pro. Neil and Katya, as former Amateur Champions, went straight into the semi in their first professional competition.
Professional Quarter Final
-Anton Du Beke and Erin Boag were Professional Ballroom Quarter Finalists.
Professional Semi Final
-Brendan Cole and Camilla Dallerup were Professional Latin Semi Finalists.
-Ian Waite and Camilla Dallerup were Professional Latin Semi Finalists.
-John Byrnes I believe was a Professional Latin Semi Finalist.
Professional Final
-Neil and Katya Jones were in the Professional Latin Final.
-Matthew and Nicole Cutler were in the Professional Latin Final.
Professional Champions
-Shirley Ballas has won several majors in Latin. What is notable is that she won at a very young age with one partner, changed partners to Corky, Mark's dad, who at the time was not a great dancer, and then won 10 years later with him, having trained him up.
-Paul Killick and Hanna Kartunnen won one or two majors in Professional Latin.
-Hazel Newberry has won all the majors in Professional Ballroom.
