In fact I think the subtle difference lies in the fact of being named in the will and have part of estate bequeathed by mean of this instrument of having a legal right irrespective of what is in the will. In some counties, children in particular have a right to a quota estate other can never be denied or taken away (even by the deceased in a will)

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Note added at 19 mins (2022-10-24 13:28:47 GMT)
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https://www.law.cornell.edu/wex/heir_at_law
(though in France, for instance, you are still entitled to a minimum interest in the estate even in presence of a will, which can only add to the legal minimum)

The French is clumsy, with "seuls héritiers LEGAUX, tant LEGAUX qu'institués".

I'd say "only legal heirs, be they next of kin or devisees/legatees"

The description of 'parentèle' below gives the degrees of (nerxt of) kinship.
" Parentèles
Les héritiers sont classés en parentèles, soit en groupes de parents. La succession ne revient à une parentèle que si tous les représentants de la parentèle précédente sont décédés.
Il existe trois parentèles :
 Première parentèle : les descendants du défunt.
S'ils sont décédés, ils sont représentés par leurs descendants.
 Deuxième parentèle : les parents du défunt, chacun pour une demie.
S'ils sont décédés, ils sont représentés par leurs descendants.
 Troisième parentèle : les grand-parents du défunt, la moitié revenant à la ligne maternelle, l'autre moitié à la ligne paternelle.
S'ils sont décédés, ils sont représentés par leurs descendants.
A défaut d'héritiers de la troisième parentèle, la succession est dévolue, dans le canton de Vaud, par moitié au canton et par moitié à la commune du dernier domicile du défunt."
https://www.vd.ch/themes/justice/la-justice-civile/successio...

"The historical definition of “LEGATEE" is someone who receives personal property (as opposed to real property) from an estate, but it has come to more commonly refer to a person who inherits under a will but may not be related to the decedent (i.e. the person who has died).
The most common example would be a friend inheriting under someone's will, but a legatee may also be a charity, business, or other organization.
What Is a Devisee?
Historically speaking, a “DEVISEE" is someone who receives real property (as opposed to personal property) from an estate.
In modern times, though, a devisee usually refers to anyone who receives property by being named in a decedent's will whether they are related or not—like a friend, as described above.
[...]
Under current laws, though, the main difference between a legatee and a devisee is simply the governing state law. That is, while some states use the term “legatee" to refer to someone who inherits under a will but is not related to the decedent, other states may use “devisee," but the TERMS ARE, IN ESSENCE, INTERCHANGEABLE."
https://www.legalzoom.com/articles/legatee-heir-beneficiary-...

"DEVISEE
n. a person who RECEIVES A GIFT OF REAL PROPERTY BY A WILL. The distinction between gifts of REAL PROPERTY AND PERSONAL PROPERTY ARE ACTUALLY BLURRED, so terms like beneficiary or LEGATEE COVER THOSE RECEIVING ANY GIFT BY A WILL."
https://legal-dictionary.thefreedictionary.com/Devisee

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Note added at 3 hrs (2022-10-24 16:42:01 GMT)
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"next of kin" would be a problem in the context of British (say) inheritance since next of kin do not necessarily inherit, but under French and, as I now know, Swiss law, they do.

French term (edited): a laissé, pour seuls héritiers légaux, tant légaux qu'institués

Qestion closed very quickly for such an important topic, but I seem to have dealt with the E&W statutory trusts on intestacy DEU/ENG https://www.proz.com/kudoz/german-to-english/law-general/265... - rather than FRE/ENG.

I think the conundrum of seuls héritiers légaux, tant légaux ... can be overcome in English law by taking, again, the route of the UK Administration of Estates Act 1925 referring to 'persons entitled as on intestacy' rather than heirs or beneficiaries vs. ones directly appointed by Will *or* by half-secret or fuly secret trusts.

Low confidence level in the descending order of 4-3-2.