Here is a short summary of the various classes of Heresy era warships and specific Emperor's Children vessels that we know about:
I. Gloriana Class Flagship
Length approx. 20 km
The Gloriana-class Flagship was a massive class of vessels constructed during the height of the Great Crusade. Each of these mighty vessels was highly individualistic and unique from one another in both form and armament. During the Great Crusade each individual Space Marine Legion acquired at least one such vessel which inevitably became the Legion's flagship, utilized by their respective Primarchs.
List of known Gloriana class EC ships:
Pride of the Emperor (Fulgrim) *
The Word Bearers also produced a triumvirate of massive warships called the Abyss class that dwarfed even the Gloriana class flagships. However these ships were unique, and the Emperor's Children never possessed a ship more massive than the Pride of the Emperor.
II. Battleship or Battle Barge
Length approx 8 - 12 km
The principal (or capital) class of warship in the Great Crusade and the mainstay of the Imperial fleets is the Battleship, with more than a thousand such mighty engines of war in operation at the height of the Imperium's expansion.
Battle Barges, a development of the Great Crusade, are not a single designation or class as such, but rather a term given to any variant or refit of battleship class hull modified and optimised for use by the Legiones Astartes specifically for Space Marine planetary assault and ship to ship boarding action.
Battleships commonly hold approximately 300 space marines and support.
Noteworthy classes: Goliath, Victory, Infernus, Retribution, Imperator, Tiamat (Shield Bastion), Ironclad, Warspite (Battle Barge), Dictatus, Mortis Rex.
List of known EC Battleships:
Proudheart (Eidolon. Dictatus Class.) ***
Wage of Sin (Eidolon)
III. Grand Cruiser and Galleass of War
Length approx 6 - 8 km
A noteworthy but relative uncommon type of warship, Grand Crusaders are "pocket battleships" - something of a halfway house between a battleship and cruiser in size and firepower.
The Galleass of War is the equivalent vessel (often much larger physically), much of whose fabric is given over to freight and transport capacity, while still maintaining formidable armaments and defense.
Noteworthy Classes: Avenger, Dagon, Inflexible, Maelstrom, Odysseus (Galleass of War).
List of known EC Grand Cruisers:
Ravisher (Azael Konenos. Avenger Class.) ***
Length approx. 4 - 6 km
Light Cruisers and Heavy Cruisers are medium-sized warships intended primarily for independent military operations such as raids, outpost assaults, deep-range patrols and search and destroy missions and for use as "workhorse" warships in larger fleets and squadrons. The difference between the two primary types of cruiser is principally found not in general size but role and specialization.
Heavy (or armoured cruisers as they are also known) are designed to favor defense and firepower (particularly over gunned ships for their class may be referred to as battle cruisers).
Light cruisers sacrifice some of these elements for greatly increased speed and maneuverability.
Strike cruisers are modified designs used for planetary assault and boarding actions in primary over other roles.
Cruisers commonly hold approximately 100 space marines.
Noteworthy Classes: Arminger, Eclipse, Hades, Hellfire (Lance Cruiser), Siluria, Tetsujin, Crusade, Olympia (Strike Cruiser), Cardinal, Lunar, Bellerophon (Heavy Assault Cruiser)
List of known EC Cruisers:
Andronius (Eidolon. Strike Cruiser.) *
Infinite Variety ***
Mortal Splendour ***
Perfection's Lament ****
PhoenicianPulchritudinous, later known as Fleshmarket (Fabius Bile)
Suzerain (Cario) ***
Threat of Rapture ****
V. Escort (Frigate and Destroyer)
Length approx 0.5 - 2 km
Escort is the catch all designation for the smallest division of Warp capable warships.
The most common escort class of the Great Crusade is the Frigate, a multipurpose armed vessel designed to largely balance firepower, defense and range.
Destroyers are small escorts that are relatively heavily armed warships for their size, but commensurately ill defended and with poor independent range designated either to attack larger ships and void stations in waves or expend themselves sacrificially to protect more important vessels and convoys.
Warp Runners are designed to incorporate only minimal crew, armament and life support, sacrificing their design almost entirely for speed and range of operation, being employed principally as spy vessels, blockade runners, couriers and explorers.
Noteworthy Classes: Sword (Heavy Frigate), Thunderbolt (Heavy Frigate), Scepter, Havoc (Minekeeper), Baron (Minekeeper), Harpy (Minekeeper), Stalwart (Minekeeper), Cobra (Destroyer), Vigil (Siege Frigate), Spectre (Warp Runner), Thor (Ordinancer).
List of known EC Escorts:
Golden Mean **
** The Damnation of Pythos
*** The Path of Heaven
**** Talon of Horus