In a cover story entitled "Catherine the Great: how the crisis made Kate the kingmaker", Tatler claims to have spoken to friends and royal insiders to build a profile of the future Queen.
The society magazine has detailed the lives of the aristocracy and Royal family for more than 300 years.
Next month's issue claims to reveal how the Duchess of Cambridge is now "working as hard as a top CEO", as well as giving details of a now-famous "row" between her and the then-Meghan Markle ahead of the 2018 royal wedding.
Neither Kensington Palace nor a spokesman for the Sussexes has commented on the veracity of the claims.
It is understood that Kensington Palace was not aware of the profile ahead of publication, and a source denied that the Duchess felt "exhausted and trapped" by her duties.
One unnamed friend told the magazine: "Meghan and Harry have been so selfish. William and Catherine really wanted to be hands-on parents and the Sussexes have effectively thrown their three children under a bus. There goes their morning school runs as the responsibilities on them now are enormous."
Another said: "Kate is furious about the larger workload. Of course she's smiling and dressing appropriately but she doesn't want this. She feels exhausted and trapped. She's working as hard as a top CEO, who has to be wheeled out all the time, without the benefits of boundaries and plenty of holidays."
Since the lockdown, the Duchess has launched a photography exhibition Hold Still, and taken part in video calls to schools, hospitals and maternity services, as well as playing bingo with pensioners to highlight social care.
The Cambridges have also appeared on a Zoom call to celebrate the work of nurses, joined the "clap for our carers" movement, and cooked pasta to deliver to vulnerable locals who live near them. The Sussexes, meanwhile, are beginning a new life in Los Angeles, conducting video calls to patronages and for charities from a temporary home owned by Tyler Perry, the actor. They have been seen delivering food to those in lockdown, while baby Archie starred in a first birthday video linked with a Save the Children campaign.
One "royal insider", speaking of the differences between the Duchesses, said: "In the palace, you hear numerous stories of the staff saying so-and-so is a nightmare and behaves badly but you never hear that about Kate."
A "courtier" added: "Kate keeps her staff whereas Meghan doesn't. Doesn't that say everything?"
On the Duchess of Cambridge's character, the magazine noted that it was "difficult to get a true sense" because she was determined to "project an aura of blandness" and is seen as "impenetrable".
One member of the young royal set, it is claimed, said: "She has a ruthless survival streak, just like the House of Windsor. It's why she is so well suited. She keeps her head down because the prize of being queen is so great. She models herself on the Queen and now speaks like the Queen."
The full feature is published in Tatler, out in print and digital editions on May 28.
