Shipbucket

Nice. Maybe a good idea, though, to raise the height of the fore funnel to reduce smoke interference on bridge personnel. A couple of ventilators for the midships boiler room may be helpful also.

More boats and cranes for them?

I totally love that collier! Maybe one day I'll "steal" it for my AU! Awesome! As for the cruiser, I strongly encourage you to finish it in your present layout. (adding quite a few more ventilators and cowls, though...), since it's, I believe, a sign of a gifted AU-creator to allow imperfection to be shown, such as the troubled height of the cruiser's funnels! You can eventually draw a rebuilt or refitted version with heightened funnels and a few more changes... Straight-away perfection is only for the implausible! Yours is very plausible right now...

I really like that forward layout on Cape; you have three guns firing directly forward without having to superfire any of them. My only concerns are that they're a bit close so a hit might very well take out more than one gun and being that close together makes mount and hoist a bit problematical. The crews might be a bit crowded as well.

I have to say I'm not sold on the collier. Given the timeframe and choice of building material, you're pretty much forced to have the engine amidships. Once you start to unload her the bow is going to come up out of the water and the stern is going to settle deeper which will put an enormous load on the keel. The only way to counter this is with ballast tanks and they don't really work with wooden hulls.
Speaking of wood, I'd abandon it as fast as I could get away with and built her out of steel. Wood has many great qualities, but it's expensive to build ships with it and even more expensive to maintain those boats.
I'd add a fo'c'sle. Flush-decked steam ships in this size-range wasn't really a thing at the time, plus it'll make coaling operations much easier since it'll be the roughly the same height as the receiving ships deck. I'd also add proper bulwarks instead of railings since it's much more suitable to the timeframe. Except for the area abeam the coal hatches.
Lastly you'll need at least two feet of clear space all the way around the hatches since they were sealed by stretching canvas across them that was held in place with wooden boards (Battens) that were nailed to the side of the hatch coaming. Hence the term batten down the hatches.

Lovely ideas about the Cape class and collier.
I'll join Thiel's remarks about the collier, though, and add some.
As mentioned the colliers of that era had their engines midships, and usually had 4 hatches/holds (or 4 hatches and 2 large holds).
The derricks on the mast ought to be much lower. As they are now, it was more common with lumber carriers (as they usually had large amount of logs as deck cargo). Also note that the front structure in bows is redundant, and if you raise the fo'c'sle it will obscure the view from the bridge.
As you plan your ships with a lot of British influence you'll want to consider British types of colliers to get your inspiration from.

In 1905, the Naval Commission Board convened on the matter of heavy defence. Whilst the HMVS Victoria (III) would be in service in less than 3 years, it looked certain that the newest cruiser would be armed would be soon be completed with 6 or 7.5 inch guns. Realising that said guns would be too small against larger cruisers and small capital ships, the board decided to open an investigation into the procurement of a larger ship. However restrictions were found into this idea mainly navigation and logistics. Among these is a need for a draft less than 9 m and the need to be coal-fired to conform with the availability of Latrobe Valley coal. This saw a flurry of design submitted that ranged from 8,000 tons to a full 24,000 tons. Ultimately the idea was until 1907 when the board reconvened to discuss finalising limits with the Royal Navy. This led to series of delegations traveling to and from London, Which led to a basic set of parameters being :

*170 m long 25 m wide 8 m deep ( being the maximum size Capable of being handled by the Alfred Graving Dock after a planned extension)

*radius of 3000 nautical miles

*Main armament ranging between 12 to 15 inches (A minimum of four individual guns in at least two turrets)

*Be provided with triple expansion turbines

*Adequate armour to withstand medium-sized calibre projectiles with enough protection to ensure vital protection against large calibres, up to and including 12 inch shells for larger designs( bearing in mind the growth of Japanese and South American capital ships in regards to calibres)

Wary of the Ibuki class from Japan which mounted four 12 inch guns, between government decided to bring the planning phase up as much as possible, However this is only occurred in 1911, branching out into eight designs. At this point the government started to question the need for such a large, expensive and labour intensive ship. The board soldiered with on the proposal until 1913 when it was dropped in favour of up-gunning the Victoria's 7.5 inch guns to 9.2 inch variants instead. This was accomplished in 1914 as hostilities broke out in Europe