I'm not fammilar with TB warlords, and Spellforce does not appear to like me. However!
The main map is, at its most basic level, just a mission selection screen. Select a zone, then a choice of missions, shops, recruitments and upgrades are available. Not all zones are available first off, they become available when certain missions are completed. At this point, it's turn based... but no enemy movements are made aside from a journal clock that tracks your progress on how many game days it takes to finish it ;)
(Not an actual clock, you can leave it still on the screen for a day and nothing will change)
Some missions are in parts, they unlock when you complete others. The Main Quest, will have you exploring pretty much the whole main map. Random encounters are also present.
Mission maps are your standard RTS flavour. Though there are 4 different resources, and a huge amount of hero combinations to play through. Most are 'kill all opponents' theough there is some variety 'most raised buildings' 'most killed number of enemies' 'retrieve the doflicky' and so on.
The RPG-ness comes in from that your hero character and surviving troops (limited) can be taken into new missions, slowly upgrading to become more powerful. However, all but the hero character can actually die. Once a troop member is gone, it is gone for good.
Items, including 'set' pieces can be taken between missions. You can restart the campaign at any point, with your kitted out high level hero and eventually the game changes from an RTS to a hack'n'slash. At this point, it's best to upp the difficulty, or move to multiplayer and skirmish modes.
edit: I should also point out, the game is a bit of a 'huh? 3am already' type of game in the addiction level for me. One of the most surprising titles here I've played in terms of enjoyment .
Post edited May 21, 2009 by Ois