‘Ice’ is an overlay of the ‘Default’ theme which is free to download and use. See all available themes here – https://simple-press.com/store/themes/
The Default theme is getting a bit long in the tooth and has largely been superceded by more up to date and mobile friendly themes like Reboot, Unified and BareBones.
BareBones does not come with any overlays as it has a built in customiser that allows you to set what main colours you prefer so overlays are not required. BareBones is also – as the name implies – a simple and basic theme which, to some degree, mimics the more simple styling of plugins like bbPress but still retains the advanced features of SP. The other feature of BareBones is being simple – it is also a fast loader and quick to display.
If you want to style more than the colours in BareBones then you can, of course, create a child theme from it (frameworks also free to download) and add your own replacement CSS rules.
As to creating forums (in the admin) and topics and posts (in the public front-end) then having used a number of forums in the past myself In don’t fully understand why you should find it so complicated. ‘New Topic’ and ‘Add Reply buttons/links (dependent upon theme) are, surely, pretty self-explanatory!
What SP does offer – and can seem somewhat complex at first sight – is a very rich set of options and settings. But for a basic forum you are probably safe leaving them al as defaults from the install. But getting to know them and using the popup help against each section will open up many possibilities for the more advanced and, perhaps serious, forums.