The generation options I currently have for the profile I've set as default (and yes, I have checked that I'm using the right profile) are as follows;

{"coordinateScale":175.0,"heightScale":75.0,"lowerLimitScale":512.0,"upperLimitScale":512.0,"depthNoiseScaleX":200.0,"depthNoiseScaleZ":200.0,"depthNoiseScaleExponent":0.5,"mainNoiseScaleX":165.0,"mainNoiseScaleY":106.61267,"mainNoiseScaleZ":165.0,"baseSize":8.267606,"stretchY":13.387607,"biomeDepthWeight":1.2,"biomeDepthOffset":0.2,"biomeScaleWeight":3.4084506,"biomeScaleOffset":0.0,"seaLevel":63,"useCaves":true,"useDungeons":true,"dungeonChance":7,"useStrongholds":true,"useVillages":true,"useMineShafts":true,"useTemples":true,"useMonuments":true,"useRavines":true,"useWaterLakes":false,"waterLakeChance":49,"useLavaLakes":true,"lavaLakeChance":80,"useLavaOceans":false,"fixedBiome":-1,"biomeSize":6,"riverSize":8,"dirtSize":33,"dirtCount":10,"dirtMinHeight":0,"dirtMaxHeight":256,"gravelSize":33,"gravelCount":8,"gravelMinHeight":0,"gravelMaxHeight":256,"graniteSize":33,"graniteCount":10,"graniteMinHeight":0,"graniteMaxHeight":80,"dioriteSize":33,"dioriteCount":10,"dioriteMinHeight":0,"dioriteMaxHeight":80,"andesiteSize":33,"andesiteCount":10,"andesiteMinHeight":0,"andesiteMaxHeight":80,"coalSize":85,"coalCount":4,"coalMinHeight":0,"coalMaxHeight":128,"ironSize":45,"ironCount":4,"ironMinHeight":0,"ironMaxHeight":64,"goldSize":18,"goldCount":1,"goldMinHeight":0,"goldMaxHeight":32,"redstoneSize":32,"redstoneCount":2,"redstoneMinHeight":0,"redstoneMaxHeight":16,"diamondSize":8,"diamondCount":1,"diamondMinHeight":0,"diamondMaxHeight":16,"lapisSize":16,"lapisCount":1,"lapisCenterHeight":16,"lapisSpread":16}

The ore settings are, however, being ignored, and ores are generating at vanilla sized veins. I also checked the log for any errors that might indicate I messed up the preset somehow, but couldn't find any.

Can you show me the full config please?

Full config is here; https://pastebin.com/MykM0LBT

Have I screwed anything up?

I will check it out later. Seems to be ok